U.S. patent application number 17/147599 was filed with the patent office on 2021-07-15 for system and method for monitoring offset during navigation-assisted surgery.
This patent application is currently assigned to Stryker Corporation. The applicant listed for this patent is Stryker Corporation. Invention is credited to Zachary Bolthouse, James G. Walen.
Application Number | 20210212769 17/147599 |
Document ID | / |
Family ID | 1000005348306 |
Filed Date | 2021-07-15 |
United States Patent
Application |
20210212769 |
Kind Code |
A1 |
Walen; James G. ; et
al. |
July 15, 2021 |
System And Method For Monitoring Offset During Navigation-Assisted
Surgery
Abstract
Surgical systems and methods for tracking physical objects near
a target site during a surgical procedure are provided, the
surgical system employs a navigation system and a surgical
instrument; an instrument tracker is provided on the surgical
instrument and a patient tracker is provided on the patient's
target tissue; the system and method is configured to detect an
error condition compromising accuracy of the navigation guidance
and to track and monitor a tool-to-bone offset.
Inventors: |
Walen; James G.; (Portage,
MI) ; Bolthouse; Zachary; (Kalamazoo, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stryker Corporation |
Kalamazoo |
MI |
US |
|
|
Assignee: |
Stryker Corporation
Kalamazoo
MI
|
Family ID: |
1000005348306 |
Appl. No.: |
17/147599 |
Filed: |
January 13, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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63054811 |
Jul 22, 2020 |
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62960218 |
Jan 13, 2020 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 34/10 20160201;
A61B 17/1757 20130101; A61B 2034/2072 20160201; A61B 2034/104
20160201; A61B 2017/00199 20130101; A61B 2034/2057 20160201; A61B
17/15 20130101; A61B 2017/00039 20130101; A61B 34/20 20160201; A61B
17/1703 20130101; A61B 2017/00398 20130101; A61B 2017/00119
20130101; A61B 2217/005 20130101; A61B 2034/2051 20160201; A61B
2034/105 20160201; A61B 2017/00123 20130101 |
International
Class: |
A61B 34/20 20060101
A61B034/20; A61B 34/10 20060101 A61B034/10; A61B 17/15 20060101
A61B017/15; A61B 17/17 20060101 A61B017/17 |
Claims
1. A method of navigating a surgical instrument having a variable
speed motor relative to a bone, the method including using a
navigation system including a localizer having a localizer
coordinate system, an instrument tracker coupled to the surgical
instrument, a patient tracker coupled to a bone, a controller in
communication with the navigation system, the controller
controlling the surgical instrument, the method comprising:
registering, with the localizer, the patient tracker in the
localizer coordinate system, defining a bone location of the bone
relative to the localizer coordinate system; registering, with the
localizer, the instrument tracker in the localizer coordinate
system, defining an instrument location of an instrument tool tip
relative to the localizer coordinate system; defining a motor
operation for the instrument when the instrument tool tip is not in
contact with the bone; monitoring, with the controller, motor
operation of the instrument during a medical procedure; monitoring,
with the navigation system, a position of the instrument tool tip
relative to the bone to determine when the instrument tool tip is
in contact with the bone in the localizer coordinate system;
comparing the motor operation to the monitored position of the
instrument tool tip; determining an error condition when the
monitored position of the instrument tool tip is in contact with
the bone in the localizer coordinate system and the monitored motor
operation equals the defined motor operation for the instrument
when the instrument tool tip is not in contact with the bone; and
triggering an action when an error condition is determined.
2. The method of claim 1, wherein defining the motor operation for
the instrument when the tool tip is not in contact with the bone
comprises defining a threshold value for power, voltage, current,
or combinations thereof, when the motor is operated while the
instrument tool tip is not in contact with bone.
3. The method of claim 1, further comprising defining a second
motor operation for the instrument when the instrument tool tip is
in contact with the bone; and determining a second error condition
when the monitored position of the instrument tool tip is not in
contact with the bone in the localizer coordinate system and the
monitored motor operation equals the second defined motor operation
for the instrument when the instrument tool tip is in contact with
the bone; and triggering a second action when the second error
condition is determined.
4. The method of claim 3, wherein triggering one of an action or a
second action comprises one of sounding an audible alert,
displaying a visual alert, activating a tactile alert, cutting off
power to the surgical instrument, or combinations thereof.
5. A method of navigating a surgical instrument having a variable
speed motor using a navigation system including a localizer having
a localizer coordinate system, an instrument tracker coupled to the
surgical instrument, a patient tracker coupled to a bone, a
controller in communication with the navigation system and
providing power to the surgical instrument, the method comprising:
registering, with the localizer, the patient tracker in the
localizer coordinate system, defining a bone location of the bone
relative to the localizer coordinate system; registering, with the
localizer, the instrument tracker in the localizer coordinate
system, defining an instrument location of an instrument tool tip
relative to the localizer coordinate system; defining a first motor
operation of the surgical instrument operating while not in contact
with the bone; monitoring, with the controller, a motor operation
of the surgical instrument during a medical procedure; monitoring,
with the navigation system, a position of the instrument tool tip
relative to the bone in the localizer coordinate system; comparing
the monitored motor operation to the defined motor operation;
determining a contact time between the instrument tool tip and the
bone when the monitored motor operation deviates from the defined
first motor operation; determining, with the navigation system at
the contact time, a tool-to-bone offset as a distance between the
instrument tool tip and a surface of the bone in the localizer
coordinate system; and triggering an action when the tool-to-bone
offset exceeds a predefined magnitude.
6. The method of claim 5, wherein triggering an action comprises
one of sounding an audible alert, displaying a visual alert,
activating a tactile alert, cutting off power to the surgical
instrument, or combinations thereof.
7. The method of claim 5, wherein the predefined magnitude is 0.5
millimeters.
8. The method of claim 5, further comprising displaying, on a
display device, the determined tool-to-bone offset.
9. The method of claim 8, wherein monitoring the position of the
instrument tool tip relative to the bone comprises tracking the
instrument location of the instrument tool tip and the location of
the bone during the medical procedure; the method further
comprising detecting, with the navigation system, each occurrence
during the operation of the monitored position of the instrument
tool tip being in contact with the surface of the bone and logging
a series of tool-to-bone offset values determined during the
medical procedure upon each occurrence.
10. The method of claim 9, further comprising displaying, on a
display device, a series of tool-to-bone offsets as one of a
serially updating value, a chart of tool-to-bone offsets over time,
or combinations thereof.
11. The method of claim 8, further comprising defining a first
level magnitude and a second level magnitude, wherein the step of
displaying the determined tool-to-bone offset comprises displaying
the determined tool-to-bone offset in a first color when the
determined tool-to-bone offset is less than the first level
magnitude, displaying the determined tool-to-bone offset in a
second color, different from the first color, when the determined
tool-to-bone offset is between the first level and the second level
magnitude; and displaying the determined tool-to-bone offset in a
third color, different from the first and the second colors, when
the determined tool-to-bone offset is greater than the second level
magnitude.
12. The method of claim 11, further comprising defining a third
level magnitude, the method further comprising disabling power from
the controller to the surgical instrument when the determined
tool-to-bone offset is greater than the third level magnitude.
13. The method of claim 5, further comprising prompting a user to
enter a value for the predefined magnitude.
14. The method of claim 5, wherein triggering an action comprises
prompting a user to update a model of the bone, and wherein
updating the model of the bone comprises contacting a resected
surface of the bone with the instrument tool tip while power is
disabled from the controller to the surgical implement.
15. A method of operating a surgical system during a surgical
operation to verify a tracking registration, the surgical system
including a navigation system including a localizer having a
localizer coordinate system, an instrument tracker coupled to a
surgical instrument, the surgical instrument including a tool tip,
a patient tracker coupled to a patient's anatomy, a control console
in communication with the localizer, the control console in
communication with data representing the surgical instrument and
data representing the patient's anatomy, the method comprising:
tracking, with the navigation system, the surgical instrument and
the anatomy and storing, with the control console, first data
representing the tracked surgical instrument and second data
representing the tracked anatomy in a common coordinate system;
determining the tool tip is within a predefined proximity to the
tracked anatomy based on the first data representing the tracked
surgical instrument and second data representing the tracked
anatomy; determining the tool tip does not depart the predefined
proximity by more than a predefined magnitude over a predefined
duration; determining an offset distance based on the first data
representing the tracked surgical instrument and the second data
representing the tracked anatomy; comparing the offset distance to
a predefined threshold; and triggering an action when the offset
distance is greater than the predefined threshold.
16. The method of claim 15, further comprising prompting a user to
verify a tracking registration by one of displaying a prompt on a
display; sounding an audible alert; generating a haptic sensation;
or combinations thereof.
17. The method of claim 15, wherein determining the tool tip is
within a predefined proximity to the anatomy includes defining a
surface area of the anatomy not to be resected, and determining the
tool tip is within a predefined proximity to the defined surface
area.
18. The method of claim 15, wherein the offset distance is defined
as a magnitude of minimum separation between the tool tip and the
tracked anatomy in the common coordinate system, or as a magnitude
of greatest overlap between the tool tip and the tracked anatomy in
the common coordinate system.
19. The method of claim 15, wherein determining the tool tip is
within a predefined proximity to the tracked anatomy includes the
surgical instrument positioned at a first pose with respect to the
tracked anatomy, the surgical instrument defining a first proximal
point of the tool tip and wherein determining the offset distance
includes determining a first offset distance; the method further
comprising determining the tool tip is within a predefined
proximity to the tracked anatomy including the surgical instrument
positioned at a second pose with respect to the tracked anatomy,
the surgical instrument defining a second proximal point of the
tool tip and wherein determining the offset distance includes
determining a second offset distance; and wherein comparing the
offset distance to a predefined threshold includes comparing the
first offset distance to the predefined threshold, and comparing
the second offset distance to the predefined threshold, and wherein
initiating an action includes initiating an action when the first
offset distance, the second offset distance, or both the first and
second offset distances are greater than the predefined
threshold.
20. The method of claim 19, wherein the surgical instrument
includes an elongated aspect terminating at the tool tip, the
elongated aspect defining a longitudinal axis extending
substantially parallel to the elongated aspect; and wherein the
second proximal point is at least 90.degree. from the first
proximal point relative to a rotation about the longitudinal
axis.
21. The method of claim 19, wherein the surgical instrument
includes the tool tip having a spherical aspect defining a
centerpoint, wherein the second proximal point is at least
90.degree. away from the first proximal point relative to a
rotation about the centerpoint.
22. The method of claim 15, wherein triggering an action includes
one of sounding an audible alert, displaying a visual alert,
activating a tactile alert, cutting off power to the surgical
instrument or combinations thereof.
23. The method of claim 15, wherein the predefined threshold
includes a first predefined threshold, and a second predefined
threshold, and wherein triggering an action of the navigation
system includes triggering a first action when the offset distance
is greater than the first predefined threshold but less than the
second predefined threshold, and triggering a second action when
the offset distance is greater than the second predefined
threshold, wherein the first action includes one of sounding a
first audible alert, displaying a first visual alert, activating a
first tactile alert or combinations thereof and wherein the second
action includes one of sounding a second audible alert, displaying
a second visual alert, activating a second tactile alert or
combinations thereof.
24. A method of providing navigation guidance for a surgical
procedure using a navigation system, the navigation system
comprising a localizer, the method comprising: registering a
patient's anatomy in a common coordinate system, the patient's
anatomy including at least a first bone and a second bone;
registering a surgical instrument in the common coordinate system,
the surgical instrument comprising a tool tip; tracking the
patient's anatomy and the surgical instrument with the navigation
system during operation of the surgical instrument on the first
bone of the patient's anatomy; determining the tool tip is within a
predefined proximity to the second bone; determining the tool tip
does not depart the predefined proximity by more than a predefined
magnitude over a predefined duration; determining an offset
distance based on tracked position of the surgical instrument and
the second bone; comparing the offset distance to a predefined
threshold; and triggering an action when the offset distance is
greater than the predefined threshold and tracking the patient's
anatomy and the surgical instrument with the navigation system
during operation of the surgical instrument on the second bone of
the patient's anatomy.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and all the benefits of
U.S. Provisional Patent Application No. 63/054,811, filed Jul. 22,
2020; and U.S. Provisional Patent Application No. 62/960,218, filed
Jan. 13, 2020, the entire contents of which are hereby incorporated
by reference.
BACKGROUND
[0002] The present disclosure generally relates to
computer-assisted surgery. More specifically, a system and
technique for calculating an offset between a monitored position of
a surgical device relative to a patient is disclosed. The technique
may be implemented as a method, as a computer-program
non-transitory media, as a computing device, and as a system for
computer assisted surgery.
[0003] Navigation-assisted surgery is often conducted based on
pre-operatively imaged patient anatomy, utilizing one or more of
magnetic resonance imaging (MRI), computerized tomography (CT),
X-ray, or other imaging technology. Data generated through these
techniques can be very accurate and provide a basis for generating
a virtual three-dimensional (3D) model of the subject anatomy
stored in the memory in a navigation system or in communication
with the navigation system. During navigation-assisted surgery, a
patient tracker can be associated with the patient's anatomy and a
tool tracker can be associated with the surgical tool. The
navigation system can locate and track the anatomy and the surgical
tool based on the associated trackers in a virtual space of the
navigation system to provide critical information to the surgeon or
other medical professionals during the surgery.
[0004] Surgical navigation systems are used in industrial,
aerospace, and medical applications to precisely locate and track
physical objects in space and orientation. In the medical field
specifically, navigation systems can assist surgeons or other
medical professionals in precisely placing surgical instruments
relative to a target site in a patient, for example, during a
surgical operation. The target site usually requires some form of
therapy or treatment, such as tissue removal. Conventional
navigation systems employ a localizer, including one or more
sensors that cooperate with trackers to provide position and/or
orientation data associated with the surgical information and the
target site, e.g., the volume of tissue requiring treatment. These
trackers allow a surgeon to see the position and/or orientation of
the surgical tool overlaid on a monitor in conjunction with a
virtual representation of the tool and the anatomy based on
preoperative or intraoperative imaging of the patient. These
tracker also allow the navigation system to monitor the relative
positioning of the tool and the anatomy to alert the user when the
tool approaches or enters an undesirable position relative to the
anatomy. For example, to alert the user that the tool is nearing or
contacting patient tissue that is not intended to be contacted by
the tool.
[0005] The localizer is usually placed so that it has a field of
view of the trackers, that is, the localizer is positioned so that
the target site of the patient is within the target space of the
localizer. The trackers include identifiable arrays of fiducials or
markers that are fixed to at least one of a surgical instrument or
a patient to move in concert with the surgical instrument or the
patient, respectively. From the detected position of the trackers,
the surgical navigation system can determine the position and
orientation of the surgical instrument or patient and monitor the
determined position and orientation for changes over time. The term
position refers to the 3D coordinate values of an object's
coordinate system relative to a reference coordinate system used by
the surgical navigation system. The term orientation refers to the
pitch, roll and yaw of the object's coordinate system relative to
the reference coordinate system. Collectively, the position and the
particular pitch, roll, and yaw values of a given orientation may
be referred to as the object's pose in the reference coordinate
system. When both the position and orientation (or pose) are
defined, the object is known to and trackable by (i.e., registered
by) the surgical navigation system.
[0006] The tracker attached to the patient and the tracker attached
to the tool are rigidly secured to the bone and the tool applying
the treatment, thereby maintaining a fixed relationship with
respect to the target site and tool owing to the rigid nature of
the bone or tool, the rigid structure of the tracker, and the fixed
securement therebetween. In alternatives known in the art, trackers
may be deformable, affixed to flexible tissues such as skin, where
the tracker comprises a pattern or arrangement of markings,
markers, or fiducials, according to a known deformation that
provides similar information as rigid trackers. By using separate
trackers on the surgical tool and on the patient, the treatment end
of the surgical instrument can be precisely positioned at the
target site by the surgeon aided by the navigation system.
[0007] During an initial phase of the operation, an object, whether
a surgical tool or a patient's anatomy, must be calibrated or
registered to the surgical navigation system. The process of
calibration or registration refers to establishing a relationship
between the physical object and its tracker to virtual
representations of the object and tracker as data within the
surgical navigation system--that is, virtual object data and
virtual tracker data, respectively. The virtual data, whether for
the object or the tracker, may or may not be a model of the object.
Rather, the virtual data may comprise information sufficient to
identify or designate certain points of interest and may further
include other information about the dimensional characteristics of
the object. The virtual data may be established pre-operatively or
intra-operatively. The virtual data may be based on pre-existing
modeling or object specification data, or may be based on imaging
of the object in situ. The virtual data may be generated from
imaging data through a process of segmentation. For example,
pre-operative imaging of a patient's anatomy may be used to
generate a 3D model of that anatomy as virtual object data in the
memory and virtual environment of the surgical navigation system.
Likewise, a surgical tool may be manufactured according to known
geometry and structure. This geometry and structure may be
represented in a 3D model of that tool as virtual object data in
the memory and virtual environment of the surgical navigation
system. To perform the calibration, additional reference pointers
or frames having additional tracker fiducial arrays may be required
to touch off reference points according to a registration or
calibration system. Alternatively, calibration may be established
using optical processes, using projected light patterns, optical
recognition, or other conventional methods.
[0008] The localizer is typically provided with multiple sensing
technologies variously adapted for beneficial use in a particular
aspect of the operation. In one example, a localizer may be
provided with one or more sensors adapted for navigation. The one
or more navigation sensors may be adapted for navigation by
operating a high frequency of sensing cycles to accurately track
small movements over small increments of time--i.e., providing a
high resolution of tracking data.
[0009] The localizer may be further provided with sensors adapted
for machine vision or other applications beneficial to the
operation. For example, the localizer may be provided with one or
more optical cameras to provide video recording of the surgical
operation. The localizer may include multiple sets of discrete
sensors that perform different functions, that is, sense different
physical properties or light, electromagnetic energy, or other
characteristics. The data representing the sensor output of the
localizer may be processed to derive important information about
the surgical site within the field of view or range of the
localizer.
[0010] Conventional surgical navigation systems may be adapted for
use with a robotic arm or manipulator supporting the surgical tool
used during the medical operation. Incorporating the robotic arm
manipulator with the navigation system provides a further degree of
control such that movement of the surgical tool is accomplished by
or with the help of the robotic arm to ensure the proper placement
of the tool relative to the anatomy. Joint encoders or other
sensing technology can be incorporated into the robotic arm to
provide additional data to determine the location of the tool while
it is being tracked with the navigation system. This information
can be compared, and if a discrepancy arises, the operator can be
alerted, and the surgical operation halted until the error can be
diagnosed and corrected.
[0011] Improvements in surgical navigation systems adapted for use
without the assistance of a robotic manipulator are needed.
Excluding the closed loop of data provided by the robotic system
introduces additional uncertainty, leaving open the risk that the
navigation system loses calibration or registration to the tool or
anatomy trackers without the ability to detect such loss of
calibration or registration and without alerting the user. This can
lead to the potential improper placement of the tool relative to
the anatomy during the operation. Thus, there is a need in the art
for systems and methods that address the shortcomings of
conventional navigation systems, providing an effective technique
for monitoring an offset during navigation assisted surgery.
SUMMARY
[0012] A method of navigating a surgical instrument having a
variable speed motor relative to a bone is provided. The method
includes using a navigation system including a localizer having a
localizer coordinate system. An instrument tracker is coupled to
the surgical instrument. A patient tracker is coupled to the bone.
A controller is in communication with the navigation system. The
controller controls the surgical instrument.
[0013] The method includes registering, with the localizer, the
patient tracker in the localizer coordinate system, the
registration defining the location of the bone relative to the
localizer coordinate system. The method includes registering, with
the localizer, the instrument tracker in the localizer coordinate
system, the registration defining the location of an instrument
tool tip relative to the localizer coordinate system.
[0014] The method includes defining a motor operation for the
instrument when the instrument tool tip is not in contact with the
bone. The method includes monitoring, with the controller, motor
operation of the instrument during a medical procedure and
monitoring, with the navigation system, a position of the
instrument tool tip relative to the bone to determine when the
instrument tool tip is in contact with the bone in the localizer
coordinate system.
[0015] The method includes comparing the motor operation to the
monitored position of the instrument tool tip; and determining an
error condition when the monitored position of the instrument tool
tip is in contact with the bone in the localizer coordinate system
and the monitored motor operation equals the defined motor
operation for the instrument when the instrument tool tip is not in
contact with the bone. The method includes triggering an action
when an error condition is determined.
[0016] In the method, the step of defining the motor operation for
the instrument when the tool tip is not in contact with the bone
may include defining a threshold value for power, voltage, current,
or combinations thereof, when the instrument motor is operated
while the instrument tool tip is not in contact with bone. The step
of defining the motor operation may include storing data
representing the motor operation in a memory of one or more of the
controller, the navigation system, the surgical instruments, or
combinations thereof.
[0017] The method may also include the step of defining a second
motor operation for the instrument when the instrument tool tip is
in contact with the bone. Defining a second motor operation, the
method may further include determining a second error condition
when the monitored position of the instrument tool tip is not in
contact with the bone in the localizer coordinate system and the
monitored motor operation equals the second defined motor operation
for the instrument when the instrument tool tip is in contact with
the bone. The method may also include triggering a second action
when the second error condition is determined.
[0018] In the method, the step of triggering one of an action or a
second action comprises one of sounding an audible alert,
displaying a visual alert, activating a tactile alert, cutting off
power to the surgical instrument, or combinations thereof.
[0019] A method of navigating a surgical instrument having a
variable speed motor relative to a bone and monitoring a
tool-to-bone offset is provided. The method includes using a
navigation system including a localizer having a localizer
coordinate system. An instrument tracker is coupled to the surgical
instrument. A patient tracker is coupled to a bone. A controller is
in communication with the navigation system and controls the
surgical instrument.
[0020] The method includes registering, with the localizer, the
patient tracker in the localizer coordinate system, the
registration defining the location of the bone relative to the
localizer coordinate system. The method includes registering, with
the localizer, the instrument tracker in the localizer coordinate
system, the registration defining the location of an instrument
tool tip relative to the localizer coordinate system.
[0021] The method includes defining a first motor operation of the
surgical instrument operating while not in contact with the bone.
The method includes monitoring, with the controller, a motor
operation of the surgical instrument during a medical procedure;
and monitoring, with the navigation system, a position of the
instrument tool tip relative to the bone in the localizer
coordinate system.
[0022] The method includes comparing the monitored motor operation
to the defined motor operation; and determining a contact time
between the instrument tool tip and the bone when the monitored
motor operation deviates from the defined first motor operation.
The method includes determining, with the navigation system at the
contact time, a tool-to-bone offset as a distance between the
instrument tool tip and a surface of the bone in the localizer
coordinate system. Although described herein as a tool-to-bone
offset, it should be appreciated that the reference to "bone" is
not intended to be limiting, and the use of "bone" in this way can
be understood as any type anatomical structure upon which a
surgical operation is performed and includes non-bone type tissues,
such as skin, muscle, connective tissues, nervous tissues, and
others. The method includes triggering an action when the
tool-to-bone offset exceeds a predefined magnitude.
[0023] In the method, the step of triggering an action may include
one of sounding an audible alert, displaying a visual alert,
activating a tactile alert, cutting off power to the surgical
instrument, or combinations thereof. In the method, the predefined
magnitude may be equal to 0.5 millimeters. The step of triggering
an action may include prompting a user to update a model of the
bone, and the method may include the step of updating the model of
the bone. The step of updating the model includes contacting a
resected surface of the bone with the instrument tool tip while
power is disabled from the controller to the surgical
implement.
[0024] The method may further include displaying, on a display
device, the determined tool-to-bone offset. The method may include
displaying the series of tool-to-bone offsets as a chart of offset
values over time.
[0025] In the method, the step of monitoring the position of the
instrument tool tip relative to the bone may include tracking the
location of the instrument tool tip and the location of the bone
during the medical procedure; and may further include detecting,
with the navigation system, each occurrence during the operation of
the monitored location of the instrument tool tip being in contact
with the surface of the bone and logging a series of tool-to-bone
offset values determined in the course of the medical procedure
upon each occurrence. The method may further include displaying, on
a display device, the series of tool-to-bone offsets as a
continuously updating value.
[0026] The method may further include defining a first level
magnitude and a second level magnitude. In the method the step of
displaying the determined tool-to-bone offset may include
displaying the offset in a first color when the offset is less than
the first level magnitude, displaying the offset in a second color,
different from the first color, when the offset is between the
first level and the second level magnitude; and displaying the
offset in a third color, different from the first and the second
colors, when the offset is greater than the second level magnitude.
The predefined magnitude for triggering an action may be equal to
the second level magnitude. The predefined magnitude for triggering
an action may be greater than the second level magnitude. The
method may further include defining a third level magnitude,
wherein the method also includes disabling power from the
controller to the surgical instrument when the tool-to-bone offset
is greater than the third level magnitude. The method may include
prompting a user to enter a value for the predefined magnitude, the
first level magnitude, the second level magnitude, the third level
magnitude, or combinations thereof. The method may include
disabling power from the controller to the surgical instrument when
the tool-to-bone offset is greater than the predefined value.
[0027] A surgical system is provided. The surgical system includes
a surgical instrument having a variable speed motor, or actuator,
and a tool tip. The surgical system includes a controller for
providing power to the surgical instrument, the controller operable
to monitor a motor, or actuator, operation of the instrument, the
controller comprising a processor and a memory, the memory operable
to store information, including information representing the
operation of the instrument. The system includes an instrument
tracker coupled to the instrument and a patient tracker to be
coupled to a bone.
[0028] The system includes a navigation system comprising a
localizer. The navigation system is operable to store information
representing the surgical instrument, and information representing
the bone, in a virtual space. The navigation system is operable to
track the location of the instrument and the bone in the virtual
space during the operation based on information gathered by the
localizer. The localizer is operable to register a location of the
instrument tracker and a location of the patient tracker relative
to a localizer coordinate system, and to gather information about
the location of the instrument and the bone in cooperation with the
instrument tracker and the patient tracker, respectively. The
controller and the navigation system are in electronic
communication and configured to cooperate. The controller and the
navigation system determine, based on a change in the operation, a
time of contact between the tool tip and the bone. The controller
and the navigation system determine, at the time of contact, a
tool-to-bone offset as a distance between the tracked location of
the tool tip and the tracked location of the bone. The system also
includes an alert device, wherein the controller and the navigation
system are further configured to trigger an action when the
tool-to-bone offset is greater than a predefined magnitude.
[0029] A method of operating a surgical navigation system during a
surgical operation to verify a tracking registration is provided.
The surgical navigation system includes a localizer having a
localizer coordinate system. An instrument tracker is coupled to a
surgical instrument. The surgical instrument includes a tool tip. A
patient tracker is coupled to a patient's anatomy. A control
console communicates with the localizer. The control console
communicates with data representing the surgical instrument and
data representing the patient's anatomy.
[0030] The method includes tracking the surgical instrument and the
anatomy with the navigation system and storing first data
representing the tracked surgical instrument and second data
representing the tracked anatomy in a common coordinate system with
the control console. The method includes determining the tool tip
is within a predefined proximity to the tracked anatomy based on
the tracked surgical instrument and the tracked anatomy. The method
includes determining the tool tip does not depart the predefined
proximity by more than a predefined magnitude over a predefined
duration. The method includes determining an offset distance based
on the first data representing the tracked surgical instrument and
the second data representing the tracked anatomy. The method
includes comparing the offset distance to a predefined threshold;
and triggering an action of the navigation system when the offset
distance is greater than the predefined threshold.
[0031] Optionally, the method includes prompting a user to verify a
tracking registration by one of displaying a prompt on a display;
sounding an audible alert; generating a haptic sensation; or
combinations thereof.
[0032] In the method, the step of determining that the tool tip is
within a predefined proximity to the anatomy may include defining a
surface area of the anatomy not to be resected and determining the
tool tip is within a predefined proximity to the defined surface
area.
[0033] In the method, the offset distance may be defined as a
magnitude of minimum separation between the tool tip and the
tracked anatomy in the common coordinate system, or as a magnitude
of greatest overlap between the tool tip and the tracked anatomy in
the common coordinate system.
[0034] In the method, determining the tool tip is within a
predefined proximity to the tracked anatomy may include the
surgical instrument positioned at a first pose with respect to the
tracked anatomy, and the surgical instrument may define a first
proximal point of the tool tip and determining the offset distance
may include determining a first offset distance. The method further
includes determining that the tool tip is within a predefined
proximity to the tracked anatomy and includes the surgical
instrument positioned at a second pose with respect to the tracked
anatomy, where the surgical instrument may define a second proximal
point of the tool tip and where determining the offset distance may
include determining a second offset distance.
[0035] The step of comparing the offset distance to a predefined
threshold may include comparing the first offset distance to the
predefined threshold and comparing the second offset distance to
the predefined threshold. The step of initiating an action
therefore may include initiating an action when the first offset
distance, the second offset distance, or both the first and second
offset distances are greater than the predefined threshold.
[0036] The surgical instrument may include an elongated aspect
terminating at the tool tip, the elongated aspect defining a
longitudinal axis extending substantially parallel to the elongated
aspect; and wherein the second proximal point is at least
90.degree. from the first proximal point relative to a rotation
about the centerline. The surgical instrument may include the tool
tip having a spherical aspect defining a centerpoint, wherein the
second proximal point is at least 90.degree. away from the first
proximal point relative to a rotation about the centerpoint.
[0037] The step of determining that the tool tip is within a
predefined proximity to the tracked anatomy may include the
surgical instrument being positioned at a third pose with respect
to the tracked anatomy. The surgical instrument may define a third
proximal point, the third proximal point being different from the
first proximal point and different from the second proximal point.
The step of determining the offset distance may include determining
a third offset distance.
[0038] The step of comparing the offset distance to a predefined
threshold may include comparing the first offset distance to the
predefined threshold, comparing the second offset distance to the
predefined threshold, and comparing the third offset distance to
the predefined threshold. The step of initiating an action may
include initiating an action when the first offset distance, the
second offset distance, the third offset distance or combinations
thereof are greater than the predefined threshold.
[0039] The step of triggering an action may include one of sounding
an audible alert, displaying a visual alert, activating a tactile
alert, cutting off power to the surgical instrument or combinations
thereof.
[0040] The predefined threshold may include a first predefined
threshold, and a second predefined threshold. The step of
triggering an action of the navigation system may include
triggering a first action when the offset distance is greater than
a first predefined threshold but less than the second predefined
threshold and triggering a second action when the offset distance
is greater than the second predefined threshold. The action may
include one of: sounding an audible alert, displaying a visual
alert, activating a tactile alert, cutting off power to the
surgical instrument or combinations thereof.
[0041] A surgical system is provided, including a navigation system
comprising a control console and a localizer. The navigation system
is in communication with first data representing a surgical
instrument and second data representing a patient's anatomy. The
surgical instrument includes a tool tip.
[0042] The navigation system is operable to track the surgical
instrument and the anatomy in the virtual space during an operation
based on information gathered by the localizer from an instrument
tracker coupled to the surgical instrument and a patient tracker
coupled to the anatomy. The navigation system is configured to
track the surgical instrument and the anatomy and store data
representing the tracked surgical instrument pose and the anatomy
pose in a common coordinate system.
[0043] The navigation system is configured to determine that the
tool tip is within a predefined proximity to the anatomy based on
the tracked surgical instrument pose and the tracked anatomy pose.
The navigation system is further configured to determine the tool
tip does not depart the predefined proximity by more than a
predefined magnitude over a predefined duration. The navigation
system is further configured to determine an offset distance based
on the tracked surgical instrument and the tracked anatomy in the
common coordinate system. The navigation system is further
configured to compare the offset distance to a predefined
threshold.
[0044] The navigation system may include an alert device, and the
navigation system may be further configured to trigger an action
when the offset distance is greater than the predefined threshold.
The alert device may be a footswitch, where the footswitch is
operable to generate a vibration.
[0045] A method of providing navigation guidance for a surgical
procedure is provided. The method includes registering a patient's
anatomy in a common coordinate system. The patient's anatomy
includes at least a first bone and a second bone. The method
includes registering a surgical instrument in the common coordinate
system. The method includes tracking the patient's anatomy and the
surgical instrument with the navigation system during operation of
the surgical instrument on the first bone of the patient's anatomy.
The method includes determining an offset distance according to the
methods disclosed herein with respect to the second bone; and
tracking the patient's anatomy and the surgical instrument with the
navigation system during the operation of the surgical instrument
on the second bone of the patient's anatomy.
[0046] A method of performing a surgical operation is provided. The
method includes coupling a patient tracker to a patient's anatomy
and coupling an instrument tracker to a surgical instrument, the
surgical instrument including a tool tip. The method includes
operating a navigation system to register the instrument tracker
and the patient tracker in a common coordinate system and to track
the surgical instrument and the patient's anatomy. The method
includes pausing the tool tip in contact with the patient's anatomy
for a predefined duration to initiate a registration verification.
The navigation system is configured to determine an offset distance
based on the tracked surgical instrument and the tracked patient's
anatomy. The method includes evaluating the offset distance against
a predefined threshold.
[0047] The navigation system may be configured to trigger an action
when the result of the evaluation of the offset distance determines
the offset distance is greater than the predefined threshold,
wherein the action may include one of: sounding an audible alert,
displaying a visual alert, activating a tactile alert, cutting off
power to the surgical instrument or combinations thereof. The
method may also include providing an input to the navigation system
to terminate the triggered action.
[0048] The step of pausing the tool tip in contact with the anatomy
may include pausing the tool tip in contact with a first anatomy
contact point at a first time. The surgical instrument may be in a
first pose and have a first proximal point of the tool tip being in
contact with the first anatomy contact point at the first time. The
method may further include pausing the tool tip in contact with a
second anatomy contact point at a second time. The surgical
instrument may be in a second pose and have a second proximal point
of the tool tip in contact with the first anatomy contact point at
the second time. The navigation system may be configured to
determine a first offset distance based on the first anatomy
contact point and the first proximal point, and to determine a
second offset distance based on the second anatomy contact point
and the second proximal point.
[0049] The step of evaluating the offset distance may include one
of: evaluating the first offset distance against the predefined
threshold; evaluating the second offset distance against the
predefined threshold, or combinations thereof.
[0050] The patient's anatomy may include a first bone and a second
bone, and the method may further include operating the surgical
instrument in application to the first bone and operating the
surgical instrument in application to the second bone. The step of
pausing the tool to initiate a registration verification may be
performed in contact with the second bone subsequent to operating
the surgical instrument in application to the first bone and prior
to operating the surgical instrument in application to the second
bone.
[0051] Other objects, features, and advantages of the present
disclosure will be readily appreciated as the same becomes better
understood after reading the subsequent description taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] Other advantages will be readily appreciated as the same
becomes better understood by reference to the following detailed
description when considered in connection with the accompanying
drawings, wherein:
[0053] FIG. 1 is a schematic view of a surgical system comprising a
suite of surgical tools for use in performing navigation-assisted
surgery.
[0054] FIG. 2 is a perspective view of a navigation system being
used with a surgical tool in performing navigation-assisted
surgery.
[0055] FIG. 3 shows the localizer coordinate system and a tracker
coordinate system of a tracker coupled to a surgical
instrument.
[0056] FIG. 4A shows a surgical instrument and a bone in a first
relationship.
[0057] FIG. 4B shows a representation of the navigation display for
the relationship shown in FIG. 4A in a first error condition.
[0058] FIG. 5A shows a surgical instrument and a bone in a second
relationship.
[0059] FIG. 5B shows a representation of the navigation display for
the relationship shown in FIG. 5A in a second error condition.
[0060] FIG. 6 shows a chart of actuator operation over time for a
cutting operation.
[0061] FIG. 7 is a flow chart illustrating a first method of
navigating a surgical instrument relative to a bone.
[0062] FIG. 8 is a flow chart illustrating a second method of
navigating a surgical instrument relative to a bone and determining
a tool-to-bone offset.
[0063] FIG. 9 is a flow chart illustrating a method of performing a
tracking registration verification.
[0064] FIG. 10 is a flow chart illustrating a second method of
performing a tracking registration verification.
[0065] FIG. 11 is a flow chart illustrating additional steps for
performing the tracking registration verification.
[0066] FIG. 12 shows a surgical instrument having an elongated
aspect in contact with a bone.
[0067] FIG. 13 shows a surgical instrument having a spherical
aspect in contact with a bone.
DETAILED DESCRIPTION
[0068] Referring to FIG. 1, a surgical system 10 comprising a suite
of surgical tools for use in performing navigation-assisted surgery
on a patient is illustrated. The version shown in FIG. 1 includes a
surgical navigation system 20. The surgical navigation system 20 is
set up to track movement of various objects in the operating room.
Such objects include, for example, surgical tools and patient
anatomy. The surgical navigation system 20 tracks these objects for
purposes of displaying their relative positions and orientations to
the surgeon, and in some cases, for alerting the surgeon of certain
events or occurrences in connection with operating the surgical
tools. For example, virtual cutting boundaries can be associated
with the patient anatomy and the system 10 may alert the surgeon
when a surgical tool approaches a cutting boundary or may
deactivate a tool when a surgical tool exceeds a cutting
boundary.
[0069] The navigation system 20 may include a computer cart
assembly 24 that houses a navigation computer 26. A navigation
interface is in operative communication with the navigation
computer 26. The navigation interface includes a first display 28
adapted to be situated outside the sterile field of the surgical
operation and may include a second display 29 adapted to be
situated inside the sterile field. The displays 28, 29 are
adjustably mounted to the computer cart assembly 24. One or more
input devices (not shown), such as a keyboard, mouse, trackball, or
other, can also be provided to input information into the
navigation computer 26 or to otherwise select or control certain
aspects of the navigation computer's 26 operation. Further, other
hardware may be provided to facilitate alternative forms of input.
For example, sensors may be provided at one or more of the displays
to allow input through gesture control, or a microphone may be
provided for voice command control.
[0070] A localizer 34 communicates with the navigation computer 26.
In the illustration shown, the localizer 34 is an optical localizer
and includes a camera unit 36. The camera unit 36 has an outer
casing 38 that houses one or more optical sensors 40. The optical
sensors 40 may be rigidly mounted to a common support structure.
The outer casing may provide the common support structure for the
optical sensors 40. Alternatively, a rigid support structure common
to the optical sensors may be encased by, but distinct from, the
outer casing 38. As illustrated in FIG. 1, the optical sensors 40
are disposed at opposite ends of the elongated camera unit 36, such
that the optical sensors 40 are arranged stereoscopically relative
to the surgical site.
[0071] Although described in connection with an optical localizer
including camera technology for locating and tracking an object
based on the sensing of electromagnetic energy in the visible or
near visible spectrum, other localizing and tracking technologies
may be used. For example, electromagnetic energy in the microwave
or radio wave spectrums may be used instead or in addition.
Likewise, sonic or ultrasonic energy may be another alternative
technology for locating and tracking an object. The common feature
of these technologies useful for tracking and locating an object is
that energy can be generated or reflected at the objects to be
tracked and sensed by the navigation system for determination on
the object's location.
[0072] In some alternatives, such as the one shown in FIG. 1, two
optical sensors 40 are employed. In other alternatives, additional
optical sensors may be provided, further separated from the first
set of optical sensors 40 to ensure unobstructed views of the
surgical sites and the trackers present therein. The optical
sensors 40 are capable of variable attenuation of radiant energy,
for example, light, into signals as small bursts of electrical
current that can be conveyed as information between electronic
devices.
[0073] The camera unit 36 may also, or alternatively, include a
video camera 41 or other additional sensing devices (not shown).
The video camera 41 may include similar or different optical
sensing technology as that employed in the optical sensors 40. For
example, the optical sensors 40 may be adapted to sense energy in
the infrared or near-infrared spectrum, while the video camera 41
may be adapted to send light in the visible spectrum.
[0074] The optical sensors 40 may be separate charge-coupled
devices (CCD). In some alternatives, two, two-dimensional CCDs are
employed. In some cases, the optical sensors 40 are arranged for
stereoscopic operation. In other alternatives, the optical sensors
40 may be single cameras combined with depth sensors, laser range
finders, and the like. It should be appreciated that in other
alternatives, multiple, separate camera units 36, each with a
separate CCD, or two or more CCDs, could also be arranged around
the operating room. Additional optical sensors assist in ensuring
that the navigation system 20 maintains an unobstructed view of the
surgical site through one or more of the optical sensors 40
throughout the surgical operation. The optical sensors 40 may
include CCDs capable of detecting infrared (IR) radiant energy. The
optical sensors may employ other sensing technology, including, but
not limited to, complimentary metal-oxide semiconductor (CMOS)
active-pixel sensors, and the like.
[0075] The camera unit 36 may be mounted on an adjustable arm or
other articulated support structure of the cart assembly 24 to
selectively position the localizer 34 with a field of view,
preferably unobstructed, of the target space including the surgical
site within which the patient anatomy and trackers (as discussed
below) will be positioned. In some cases, the camera unit 36 is
adjustable in at least one degree of freedom by rotating about a
rotational joint. In other alternatives, the camera unit 36 is
adjustable about two or more degrees of freedom. Where multiple
camera units 36 are employed, each may be individually mounted for
selective positioning about the surgical setting. Alternatively,
the cart structure 24 may support multiple adjustable arms to
support multiple camera units 36.
[0076] The camera unit 36 further includes a camera controller 42
in communication with the optical sensors 40 to receive signals
from the optical sensors 40. The camera controller 42 communicates
with the navigation computer 26 through either a wired or wireless
connection (not shown). One such connection may be an IEEE 1394
interface, which is a serial bus interface standard for high-speed
communications and isochronous real-time data transfer. Other
suitable connection types may include Ethernet, thunderbolt, USB
interface, PCI express, DisplayPort, or the like. The connection
could also use a company-specific or proprietary protocol. In other
alternatives, the optical sensors may communicate directly with the
navigation computer 26, such that the navigation computer
incorporates the functionality of, and thus operates as, the camera
controller 42. Processing of the signals from the optical sensors
may occur at the camera controller 42. Alternatively, the camera
controller 42 may communicate the signals to the navigation
computer 26 for processing. In communicating the signals to the
navigation computer 26 for processing, the camera controller 42 may
perform some pre-processing conditioning, reformatting,
translating, or the like.
[0077] The navigation computer 26 may be a personal computer or
laptop computer. The navigation computer 26 communicates with the
displays 28, 29, and has a central processing unit (CPU), and other
processors, memory units, data storage units and combinations
thereof. The navigation computer is provided with software as
described below. The software converts the signals received from
the camera unit 36, from the camera controller 42 or the optical
sensors 40, into data representative of the position and
orientation of the objects being tracked. Position and orientation
signals, or data derived from those signals, are used by the
navigation computer 26 for the purpose of tracking objects. The
cart assembly 24, display 28, and camera unit 36 may be like those
described in U.S. Pat. No. 7,725,162 to Malackowski, et al., issued
on May 25, 2010, entitled "Surgery System," hereby incorporated by
reference.
[0078] The surgical system 10 including the navigation system 20
may be adapted for operation with a variety of surgical tool
systems. FIG. 1 illustrates representative available tool systems,
but it should be understood that other options are available or may
become available in the future without deviation from the scope of
the present disclosure.
[0079] The surgical system 10 may be used in connection with a
cordless power tool. The cordless power tool may include a sagittal
saw, reciprocating saw, rotary drill, sternum saw, or the like. In
the illustration in FIG. 1, the cordless power tool is shown as a
cordless power driver 60. It should be understood corded power
tools may also be used. One example of such a cordless power driver
60 tool is the System 8 Cordless Driver sold by Stryker. The driver
60 includes a battery unit 61 which provides power to the driver
60. The battery unit 61 can include a rechargeable battery pack.
The battery unit 61 may be a smart battery pack, including a data
module 62 which has electronics and programming to facilitate
communication between the driver 60 and the navigation computer
26.
[0080] The driver 60 may include a driver controller 64 in
operative communication with the data module 62. Alternatively, a
single computer module may be provided that provides the
functionality of both the driver controller 64 and the data module
62. The driver controller 64 controllers the operation of the
driver 60, being in communication with input controls, such as
triggers 63, 65, the driver motor 68, and other sensors or
instrumentation included within the driver 60. In one example, a
temperature sensor is included so that an overheating driver motor
68 can be detected and operation of the driver 60 disabled by the
driver controller 64.
[0081] The driver 60 is provided with a tracker 70. The tracker 70
may be an active tracker or a passive tracker. Active trackers
require a power source and have an array of markers 72 (also
referred to as tracking elements or fiducials) that actively
generate and emit radiation in a wavelength detectable by the
optical sensors 40. The markers 72 of an active tracker may be a
light emitting diode (LED), including for example, an infrared LED.
The array of active markers may be "always on" or may be
operatively "on" to selectively fire (that is, emit radiation) in
response to commands from the surgical navigation system 20. In
such selective-fire active trackers, the tracker may communicate by
way of a wired or wireless connection with the navigation computer
26 of the surgical navigation system 20. The active tracker may be
powered with an internal battery or may have leads to receive power
from an externally-connected source.
[0082] Alternatively, the tracker 70 may be a passive tracker. That
is, the array of markers 72 may reflect ambient radiant energy or
radiant energy that has been emitted into the target space. For
example, the camera unit 36 may be equipped with one or more
infrared LEDs to emit infrared energy to be reflected by the
markers 72 and thereafter sensed by the optical sensors 40. The
passive tracker typically does not require a power source.
[0083] Although described with reference to optical technologies,
including light reflective or emitting markers, other trackers may
be used consistent with the sensing technology of the localizer.
For example, the localizer may include an electromagnetic field
generator, and the trackers may employ coils or coil arrays. An
example of the use this technology can be appreciated from the
disclosure of U.S. Pat. No. 8,249,689 B2, entitled "Coil
Arrangement for Electromagnetic Tracking Method and System," the
entirety of which is incorporated by reference.
[0084] The surgical system 10 may also be used with a universal
integrated console or an instrument platform. The universal
platform 80 comprises a console 82, a footswitch 4, and a powered
surgical instrument 86. The console 82 controls and provides power
to a connected instrument 86. The instrument 86 may be a small bone
orthopedic saw or drill, a high speed drill (for example for neuro
applications, or for spinal applications), an ENT shaver, joint
shaver, bone mill or the like. One example of such a universal
platform is the Core 2 Console powered instrument driver, and
related tools, sold by Stryker and described in the International
Application Publication PCT WO 2015/021216 A1, entitled "System And
Method For Driving An Ultrasonic Handpiece As A Function Of The
Mechanical Impedance Of The Handpiece," the entirety of which is
incorporated by reference. The console 82 includes a data module 88
which facilitates communication between the console and the
navigation computer 26.
[0085] Similar to the driver 60 described above, the instrument 86
is provided with a tracker 90. The instrument tracker 90 is similar
to the driver tracker 70 and includes an arrangement of markers 72.
The markers 72 may be active or passive, and are sensed by the
camera unit 36 to track and monitor the position and orientation of
the instrument 86.
[0086] The surgical system 10 may also be used with an ultrasonic
aspirator system 100. The ultrasonic aspirator system 100 comprises
a console 102, a footswitch 104 and aspirator tool 106. The console
102 controls and provides power to a connected aspirator tool 106.
One example of such an ultrasonic aspirator system is the SONOPET
iO Ultrasonic Aspirator sold by Stryker. The console 102 includes a
data module 108 which facilitates communication between the console
and the navigation computer 26.
[0087] The tool 106 is provided with a tracker 110, similar to the
instrument tracker 90 and the driver tracker 70. The tool tracker
110 includes an arrangement of markers 72, which may be active or
passive, as discussed above, to be sensed by the camera unit 36 for
tracking and monitoring the tool's 106 position and orientation. As
can be seen in FIG. 1, the driver tracker 70, instrument tracker
90, and tool tracker 110 are distinguishable based on their
arrangement of markers 72. Descriptions provided herein, and
designations such as "tool tracker" or "instrument tracker" are not
intended to be limiting but are simply used to differentiate among
the surgical articles available for use with the present
disclosure. The trackers may be attached in the manner shown in
U.S. Pat. No. 7,725,162 to Malackowski, et al., issued on May 25,
2010, entitled "Surgery System," the disclosure of which is hereby
incorporated by reference. Alternatively, the Trackers could be
attached like those shown in U.S. Pat. No. 9,566,120 to
Malackowski, et al., issued Feb. 14, 2017, entitled "Navigation
Systems and Method for Indicating and Reducing Line-of-Sight
Errors," the disclosure of which is hereby incorporated by
reference. In yet further alternatives, the trackers may be
attached in other ways as is conventional in the art.
[0088] Although shown as distinct structures mounted on and
extending from the surgical articles, the trackers may
alternatively be integrated into the structure of the article
itself. For example, the markers 72 may be formed directly into the
structure of the tool or instrument to be tracked. In yet further
alternatives, structures or features of the article itself may be
used as a tracker, omitting dedicated markers. In such cases,
surfaces or edges of the article may be recognizable to the
navigation system and used to track the position and orientation of
the article. Still further, markings or patterns may be included on
a surface of the article and used as a tracker. For example, a
linear barcode, or 2D barcode (also known as a QR code) can be
featured on a surface of the article that will remain visible to
the camera unit 36 throughout the surgery for tracking the
article.
[0089] Turning now to FIG. 2, the surgical system 10 is illustrated
in an exemplary surgical environment for use with a universal tool
platform 80, including console 82, footswitch 84 and instrument 86.
Also provided at the surgical site is a C-arm computerized
tomography (CT) system 120 for providing intraoperative imaging of
the patient's anatomy. Although illustrated with a CT system 120,
other imaging technology may be employed for intraoperative
imaging, including MRI, X-Ray, or videography. Generally,
regardless of the technology chosen, the imager is in communication
with the navigation computer 26. Information from the imager is
used to prepare a virtual representation of the patient's anatomy,
such as a 3D model of the tissue to be treated in the surgery. The
process of preparing the virtual representation can be through
segmentation of the image data. The segmentation can be an
automated process, for example, through machine learning. Example
processes are disclosed in U.S. Pat. No. 10,198,662 B2, issued Feb.
5, 2019, and entitled Image Analysis; and U.S. Pat. No. 8,867,809
B2, issued Oct. 21, 2014, and entitled Image Processing Method.
Using the information from the imager and affixing a further
tracker onto the tissue to be treated, the patient tracker 130, a
model of the tissue can be represented in the navigation system 20
and tracked during the course of the surgical operation.
[0090] Initially, the objects to be located and tracked during the
surgery are viewed by the optical sensors and identified. The
objects may be identified by selecting the objects to be tracked
and using an input device connected to the navigation computer 26.
The navigation computer 26 may store detailed information regarding
numerous objects in memory or data storage on the navigation
computer 26 and the user may be able to manually select the objects
to be tracked from a database of objects.
[0091] Additionally, or alternatively, the navigation computer 26
may identify the objects to be tracked based on a pre-operative
surgical plan. In this case the navigation computer 26 may have a
preset list of workflow objects that may be used in a pre-scripted
surgical workflow. The navigation computer 26 may actively search
for and locate the workflow objects using software. For instance,
groups of pixels associated with different sizes and shapes of the
various objects may be stored in the navigation computer 26. By
selecting or identifying the objects to be located and tracked, the
software identifies the corresponding group of pixels and the
software then operates to detect like groups of pixels using
conventional pattern recognition technology.
[0092] Additionally, or alternatively, the objects to be located
and tracked can be identified using an interface in which one of
the users outlines or selects the objects to be tracked on one or
more displays 28, 29. For instance, images taken by the optical
sensors 40, or a video camera, 41 of the surgical site may be
displayed on one or more of the displays 28, 29. The user then,
using a mouse, digital pen, or the like, traces objects to be
located or tracked on the display 28 or 29. The software stores the
pixels associated with the object that was traced into its memory.
The user may identify each object by a unique identifier, such as
naming the object using the software, so that the saved group of
pixels may be associated with the unique identifier. Multiple
objects could be stored in this manner. The navigation computer 26
utilizes conventional pattern recognition and associated software
to later detect these objects. The navigation system 20 is able to
detect movement of these objects by continually taking images,
reviewing the images, and detecting movement of the groups of
pixels associated with the objects.
[0093] In conventional surgical navigation systems, the objects to
be tracked are initially registered using a navigation pointer P.
For example, the navigation pointer P may have an integrated
tracker PT. The navigational computer 26 may store initial data
corresponding to the location of the tip of the pointer P relative
to the pointer tracker PT such that the navigation system 20 is
able to locate and track the tip of the pointer P in the localizer
coordinate system LCLZ. Accordingly, prior to the start of the
surgical procedure once all the objects are located in their
desired locations, one of the users may touch all of the objects
with the pointer P, while identifying the objects in the navigation
system 20 using one of the input devices described above. So, for
example, when the user touches the instrument 86 with the tip of
the pointer P the user may simultaneously trigger collection of
that point in the localizer coordinate system LCLZ (via another
input device, such as a foot pedal). When the point is collected
the user can also enter into the navigation software the identity
of the object (via typing, pull-down selection from a list of
objects, etc.).
[0094] As illustrated in the Figures, the camera unit 36 receives
optical signals from the markers 72 of the trackers 70, 90, 110,
and outputs to the navigation computer 26 signals relating to the
position of the trackers relative to the localizer 34. Based on the
received signals, the navigation computer 26 generates data
indicating the relative positions and orientations of the trackers
70, 90, 110 relative to the localizer 34.
[0095] Prior to the start of the surgical procedure, additional
data are loaded into the navigation computer 26. Based on the
position and orientation of the trackers 70, 90, 110, and the
previously loaded data, such as virtual object data representing
the geometry of the object to which the tracker is attached, the
navigation computer 26 determines the position of the working end
of the surgical article (e.g., drill point, aspirator tip, etc.)
and the orientation of the article relative to the tissue against
which the working end is to be applied.
[0096] The navigation computer also generates information that
indicates the relative position of the surgical instrument's
working end to the tissue. This information can be rendered into
useful imagery and applied to the displays 28, 29. Based on the
display, the user is able to view the relative position of the
surgical instrument working end to the tissue in the surgical site.
The displays 28, 29, as discussed above, may include a touch screen
30 or other input/output device that allows the entry of
commands.
[0097] Referring now to FIG. 3, tracking of objects in the surgical
site is generally conducted with reference to a localizer
coordinate system LCLZ. The localizer coordinate system has an
origin point and an orientation defining relative x-, y-, and
z-axes. During the surgical operation, it is preferable to keep the
localizer in a stationary position. An accelerometer (not shown)
mounted to the camera unit may be used to track sudden or
unexpected movement of the localizer coordinate system LCLZ, as may
occur when the camera unit 36 is inadvertently bumped by surgical
personnel.
[0098] Each tracker 70, 90, 110, associated with a surgical article
or a patient's anatomy has its own coordinate system separate from
the localizer coordinate system LCLZ. As depicted in FIG. 3, the
coordinate system associated with the tool tracker 90 has its own
origin point and orientation defining relative x-, y-, and z-axes.
The navigation system 20, through the localizer 34, monitors the
position and orientation of the surgical articles and the patient's
anatomy by computing the relative change of the trackers' origin
point and orientation relative to the localizer coordinate
system.
[0099] During the initial phase of the surgical procedure, the
trackers are affixed to the articles (if not provided in
manufacturing) and the anatomy to be tracked. The pose of each such
item must be mapped to the coordinate system of the tracker to that
item. This registration or calibration step creates a fixed
relationship between the virtual representation of the geometry of
the tracked article to the coordinate system of the associated
tracker. In this way, sensed movement of a tracker can be
represented virtually with a corresponding movement of the tracked
article by the navigation computer 26 relative to the other tracked
articles in the common coordinate system, for example, of localizer
LCLZ.
[0100] While navigation systems have been used with robotically
controlled surgical systems, improved method are needed to provide
navigation guidance for manually performed surgeries using powered
surgical tools. In accordance with the present disclosure an
improved method of navigating a surgical instrument is provided to
verify the position of the instrument tool tip relative to the
patient anatomy.
[0101] In a first example case, the surgical instrument includes a
variable speed motor, such as driver motor 68. The variable speed
motor is controlled by a controller. For example, the variable
speed motor may receive a control signal from the driver controller
64 in the case of the power driver 60. In another example, in the
case of the universal tool platform 80, the control signal
controlling the variable speed motor in the instrument 86 may come
from the universal console 82. The following descriptions may be
put in the context of a particular tool or tool type. This is not
intended to be limiting and the methods and systems may be
practiced with other presently-known or future developed surgical
tools, tool systems or the like. Moreover, the steps of one method
may be practiced in the context of any other method and the
features of one disclosed system may be practiced with any other
without departing from the scope of the present disclosure.
[0102] Although described in the previous paragraph with respect to
a control signal for a variable speed motor, this is not limiting,
and other alternative actuators are contemplated within the scope
of the present disclosure. For example, in the case of the
ultrasonic aspirator, a variable speed motor is not employed, but
rather a control signal from the aspirator console 102 may control
the operation of the aspirator tool 106. The aspirator tool 106
includes a hollow tip which oscillates longitudinally along its
axis, driven, for example, by a piezoelectric transducer as the
actuator of the tool. The oscillation occurs at a frequency
corresponding to ultrasound. The longitudinal vibration of the tip
destroys cell membranes by its hammering effect. Since the
high-frequency vibration generates heat, a protective sheath
carries fluid to irrigate the tip. Irrigation intensity can be
changed as needed to modulate the application of heat from the tip
to the tissue. When irrigation is low, heat developed by ultrasonic
aspiration can be used for cutting or coagulating purposes. Suction
can also be provided through the aspirator tool 106 to remove
fragmented tissue as well the irrigation through the tip. By
monitoring the operating characteristics of the control signal, the
system can detect when the tool tip is operating in free space or
is operating in contact with the tissue.
[0103] Regardless of surgical article type, operating the article
while it is in free space may be characterized differently from
operating the article while it is in contact with a patient's
anatomy, including bone or soft tissue such as skin. In the case of
a powered driver 60, or other article having a variable speed
motor, a power supplied to the motor will result in a certain
rotational speed when operating in free space. When there is
resistance applied against the rotation of the motor, such as when
a drill, bur, or other tool type, is in contact with tissue for
material removal, the rotational speed may be decreased unless the
power supplied to the motor is adjusted. For example, the current
or voltage may be increased during cutting in order to maintain a
constant rotational speed relative to when the tool is not in
contact with any tissue. Likewise, tools employing other actuators,
and not driven by a motor, may operate under a first condition when
not in contact with tissue and may operate under a second
condition, different from the first when in contact with tissue.
Such non-motor driven tools are likewise contemplated to be
practiced with the described methods and systems disclosed
herein.
[0104] The controller driving the surgical article provides the
control signal to operate the article and also is in communication
with sensors on the article to monitor the operating condition. For
example, in the power driver 60, the driver controller 64 may
receive signals indicating the driver motor's 68 instantaneous
rotational speed, applied power, voltage, current, temperature, or
otherwise. This signal may be received by the controller at a
frequency of several times per second. For example, the frequency
may be about 60 Hz, about 100 Hz, about 1000 Hz, or other suitable
frequency. In other examples, not employing a motor, such as the
ultrasonic aspirator system 100, the controller--in this case the
aspirator console 102--may receive one or more signals indicating
the operating condition of the article, i.e., the aspirator tool
106. Specifically, the aspirator console 102 may monitor the
temperature at the tool tip, the flow rate of the irrigation
through the tool tip, the vacuum applied to the suction, or
otherwise.
[0105] The controller may be equipped with memory or data storage
or may be in communication with memory or data storage, so that the
operating condition may be recorded relative to the time of the
recording. The controller may begin recording the operating
condition when the surgical article begins operating and may
continue throughout the duration of the operation. The controller
may analyze the monitored operating condition to define a first
characteristic operating condition for when the surgical article is
operating not in contact with the patient's anatomy; and may
further define a second characteristic operating condition for when
the surgical article is operating while in contact with the patient
anatomy. The monitored operating condition may be defined according
to the specific tool. For a motor driven tool, the operating
condition may be an applied power, a current, a voltage, a
rotational speed, or otherwise.
[0106] As described above, the navigation system 20 tracks and
monitors the position of the surgical article and the patient's
anatomy throughout the surgical operation. The navigation system
20, through navigation computer 26, is in communication with the
one or more controllers controlling the surgical articles employed
in the surgical operation. Utilizing the monitored operating
condition of the surgical article, the tracked position of the
surgical article can be verified, and an error condition
determined, if necessary.
[0107] The navigation system 20 maintains a virtual representation
of the surgical articles and the patient's anatomy to illustrate
and visually render their relative positions on the displays 28,
29. However, during the surgery, trackers may become displaced.
Tool wear or tissue removal from the patient may alter the fidelity
of the virtual models to their physical counterparts. Therefore,
the accuracy and the reliability of the virtual representation in
the navigation system 20 to the surgical operation may be adversely
affected. Comparing the virtual representations in the navigation
system 20 to the operating condition can provide an important
verification of the systems accuracy. Specifically, if the
navigation system 20 shows that the virtual model of the surgical
article is in contact with the patient's anatomy, but the operating
condition indicates that there is no contact between the article
and the anatomy, an error condition may be determined, and
appropriate corrective action taken.
[0108] FIG. 4A shows a surgical article and a patient's anatomy in
a first relationship where there is no contact between the surgical
article and the anatomy. In the example shown, the surgical article
is the instrument 86, and specifically, that portion of the
instrument 86 including the tool tip 87. The patient's anatomy
shown in FIG. 4A that will be the target of the surgical operation
is a bone, vertebra V. The instrument 86 may be energized by the
universal console 82, which likewise monitors parameters of the
operation of the instrument 86, including the power, voltage,
current, and/or rotational speed of the instrument 86. As shown in
FIG. 4, the instrument 86 will have a first operation that can be
characterized by the console 82 according to the monitored
parameters for operation in free space--that is, not in contact
with the bone, vertebra V.
[0109] An exemplary graph 160 of a motor operation over time is
shown in FIG. 6. In a first phase 162, the instrument is unpowered,
so the motor operation is static at the lowest level. At some time
later T.sub.1, the instrument is powered on and spins up to a first
operation state 164, before being brought into contact with the
patient's anatomy at T.sub.2. While in contact with the patient's
anatomy during the surgical procedure, the motor operation is at
the higher level 166. The instrument may be removed from contact
with the anatomy after the procedure 168 and then returned to an
unpowered state 170.
[0110] An example user interface 140 displayed by the navigation
system 20 is illustrated in FIG. 4B. The navigation system 20
computes the relationship between the instrument 86 and the bone,
vertebra V, to be in contact. The user interface 140 may be divided
into separate sections on the display with different information
displayed in the separate sections. In a first section 142 of the
user interface 140, a virtual representation of the surgical
article and the patient's anatomy is shown based on (1) the models
of those items, which may be stored in the memory of the navigation
system 26, and (2) the relevant locations of the surgical article
and the patent's anatomy that are computed based on the data sensed
by the optical sensors 40 reading the instrument tracker 90 and
patient tracker 130.
[0111] The navigation system 20 can compare the computed
relationship of the surgical article to the patient's anatomy as
being in contact or not in contact against the monitored operation
parameters to verify the accuracy of the navigation guidance. In
the example illustrated in FIGS. 4A and 4B, an error condition is
present where the navigation system 20 calculates the tool tip 87
of the instrument 86 to be in contact with the vertebra V, but the
monitored operation parameters correspond to the instrument 86
being in a relationship as shown in FIG. 4A where there is no
contact between the tool tip 87 and the vertebra V.
[0112] The navigation system 20 or the console 82 can trigger an
action in response to the determination of an error condition. A
visual alert 144 may be activated, for example, in a toolbar region
146 of the user interface 140. The visual alert 144 may be a
flashing, or blinking indicator light on the displays 28, 29. Other
visual alerts may include, in the alternative or in combination,
indicator lights on the console 82, on the computer cart assembly
24, on the camera unit 36, or elsewhere. Other visual alerts may
take the form of prompts for user action, information displays, or
other shapes, forms, pictures or otherwise.
[0113] Other actions can also be triggered in response to the
determination of an error condition. A triggered action may include
displaying specific information about the error condition,
suggesting remedial action to correct the error condition, or
combinations thereof. In FIG. 4B, error information 148 may be
displayed in a region of the user interface 140 separate from the
first section 142. The error information 148 may indicate that an
error has been detected. The error information 148 may indicate the
nature of the error--in this case that the navigation system 20 has
calculated that the instrument 86 is in contact with the bone,
vertebra V, but that the motor operation indicates that there is no
contact between the tool and the bone. The error information 148
may indicate, in the alternative or in combination, that remedial
action is advised, and further, what a preferred remedial action
may include for a particular condition. In the case where the
navigation system calculates contact between the bone and the tool,
but the motor operation indicates no contact, the remedial action
may require updating the bone model to reflect that tissue has been
removed from the bone and that the actual bone surfaces are no
longer reflected by the virtual model.
[0114] The triggered action upon detection of an error condition
may, in addition or in the alternative to the visual alert, include
other actions. The triggered action may include one or more of
sounding an audible alert, activating a tactile alert, cutting off
power to the surgical instrument, or combinations thereof. Sounding
an audible alert can include any kind of sound alarm, beep, buzzer
or the like. Displaying a visual alert may include displaying a
prompt on one or more of the displays 28, 29 of the navigation
system 20 that indicates the nature of the error condition
determined. Activating a tactile alert may include energizing a
vibratory feature of the instrument or the footswitch, or both. The
vibration may be characterized as a pattern of vibrations
associated with the type of error so that the user can distinguish
among different types of errors based on the type of vibration
alone.
[0115] FIGS. 5A and 5B illustrate another situation. In FIG. 5A,
the tool tip 87 of instrument 86 is in contact with the bone,
vertebra V. In this situation, the motor operation is at the higher
level 166 of monitored motor operation shown in FIG. 6. At time
T.sub.2, the console 82 registers that the motor operation has
deviated from the first operation state 164 corresponding to
operation in free space, that is, where the instrument 86 tool tip
87 is not in contact with the bone. The console may communicate
with the navigation computer 26 to evaluate the computed locations
for the tool tip and the bone, based on the optical sensor data
corresponding to the tool tracker 90 and the patient tracker 130 to
determine a tool-to-bone offset D. At the time T.sub.2, the
navigation system measures the distance D between the calculated
position of the tool tip 87 and the nearest surface of the bone,
vertebra V, in the direction longitudinally along the length of the
instrument 86. This distance is the tool-to-bone offset value. This
value may be displayed as a numerical measurement 150 in a region
of the display 28, 29. The system may operate to measure the
tool-to-bone offset every time that the monitored motor operation
deviates from a first level magnitude corresponding to the
operation of the instrument in free space, that is, not in contact
with the bone. This may include, for example, every time that the
motor operation transitions from a first level magnitude to a
second level magnitude corresponding to the motor operation while
the tool is in contact with the bone, as is illustrated, for
example at time T.sub.2 in FIG. 6.
[0116] Because the value of the tool-to-bone offset may change over
time as the surgical procedure progresses, the numerical
measurement 150 may be a continuously updated value changing based
on the most recent evaluation of the tool-to-bone offset. In
addition, the historical data may be recorded and displayed so that
the user can track and monitor trends in the tool-to-bone offset
and be aware as the magnitude increases to a level where the
navigation guidance cannot be relied upon to have a high level of
accuracy and remedial action may be required. For example, as
illustrated in FIG. 5B, a portion of the user interface 140
includes a graph of tool-to-bone offset values that tracks and
displays the changing value over time. The graph 152 shows the
current value at the right side of the graph, with the trend line
154 of past values scrolling toward the left side of the display.
The illustration is not intended to be limited, and other graphical
forms are contemplated without departing from the scope of the
present disclosure.
[0117] Monitoring and displaying the tool-to-bone offset may
present various ways of communicating the system status to the
user. For example, the numerical measurement 150 may be displayed
in different colors depending on the magnitude. A visual alert 144
may illuminate in different colors or blink in a varying frequency
in order to alert the user of changing conditions. The system may
be programmed with or may prompt the user to enter threshold values
for the tool-to-bone offset to trigger different types of
actions.
[0118] In one example, the tool-to-bone offset may be maintained
less than 0.50 millimeters or else trigger a responsive action like
disconnecting the instrument from power. It may be desirable to
alert the user to a changing condition before it reaches that
threshold. The numerical measurement 150 may be displayed in a
first color for values between 0.00 millimeters and 0.25
millimeters. The numerical measurement 150 may be displayed in a
second color, different from the first, for values between 0.25
millimeters up to 0.4 millimeters. The numerical measurement 150
may be displayed in a third color different from the first or
second, for values greater than 0.4 millimeters. Likewise, the
trend line may be displayed in different colors as the value
changes. The first color may be green, the second yellow, and the
third red. These illustrations are offered as examples and are not
intended to be limiting.
[0119] In either the conditions of FIGS. 4A and 4B or 5A and 5B,
the system may alert the user of an error condition and advise as
to potential remedial action. The preferred remedial action may
depend on the specific error encountered. In one example, if an
error condition arises from a broken or worn tool, the remedial
action would be to replace the tool. In another example, if an
error condition arises from displacing a tracker from its
relationship to the associated tracked object, or if the navigation
cart assembly is jostled or bumped, re-registration of the trackers
to the object in the localizer coordinate system may be the
appropriate remedial action. These illustrations are only examples
and are not intended to be limiting.
[0120] Illustrated in FIG. 7 is a first method 400 of navigating a
surgical instrument having a variable speed motor relative to a
bone. The method includes using the navigation system 20, which--as
described above--includes a localizer having a localizer coordinate
system, an instrument tracker coupled to the surgical instrument
and a patient tracker coupled to the bone. The method uses a
controller communicating with the navigation system and controlling
the surgical instrument.
[0121] In a first step 402 of the method 400 shown in FIG. 4, the
user registers the patient tracker to the bone. Registering the
patient tracker relates the patient tracker coordinate system to
the localizer coordinate system. This step also defines the
location and orientation of the bone relative to the patient
tracker so that the navigation system can track and monitor the
position and orientation of the bone based on detected movement of
the patient tracker and updating the virtual representation of the
bone in the navigation system.
[0122] In a second step 404, the user registers the instrument
tracker to the surgical instrument. Registering the instrument
tracker relates the instrument tracker coordinate system to the
localizer coordinate system. This step also defines the location
and orientation of the instrument tool tip relative to the
instrument tracker so that the navigation system can track and
monitor the position and orientation of the instrument tool tip
based on the detected movement of the instrument tracker and
updating the virtual representation of the instrument in the
navigation system.
[0123] The method includes at step 406, defining a motor operation
for the surgical instrument or article when the tool tip is not in
contact with the bone. This defining step can comprise evaluating
at least one of the power, the voltage, the current, the rotational
speed, or other operating parameter, or combination of parameters,
that characterizes the operation of the motor. Data representing
the operating parameter can be stored in a memory of the controller
controlling the operation of the surgical instrument.
Alternatively, or in addition, the data can be communicated by the
controller to the navigation system. In a further alternative or
addition, the data can be stored on a memory incorporated into the
surgical instrument itself, or another device in communication with
the instrument or console.
[0124] During a surgical operation and after an operating parameter
is analyzed to define the motor operation in free space, the method
includes the controller monitoring the motor operation of the
instrument at step 408. This monitoring can comprise periodically
receiving a signal indicating the motor operation and recording
that signal as data representing the motor operation at the time
the signal is received. In this way, the controller can create a
record of the motor operation over time during the surgical
operation.
[0125] Concurrently with monitoring the motor operation, the method
includes monitoring the position of the instrument tool tip
relative to the patient bone with the navigation system at step
410. The trackers mounted to the instrument and to the bone,
respectively, are sensed by the navigation system, and based on the
earlier registrations, the relative position of the tool tip and
bone can be determined by the navigation system and, optionally,
virtually represented on the displays. As part of monitoring the
position of the tool tip and the bone, the navigation system can
determine when contact is made between the instrument and the bone
in the localizer coordinate system.
[0126] Upon determining that contact had been made between the
instrument and the bone, the method includes, at step 412,
comparing the motor operation to the monitored position of the
instrument tool tip. The navigation system, in communication with
the instrument controller, can evaluate the motor operation of the
instrument. The evaluation considers whether the motor operation
matches the defined motor operation for the instrument when the
instrument tool tip is not in contact with the bone.
[0127] If the navigation system determines the instrument is in
contact with the bone based on the tracked positions, and the motor
operation indicates that the instrument is not in contact with the
bone at that time, the method includes, at step 414, determining an
error condition. This determination reflects that some disturbance
or aberration has entered the system. The accuracy and reliability
of the navigation system cannot be relied upon when the tracked
locations in the navigation system do not reflect the true physical
location of the instrument or bone.
[0128] Once an error condition is determined, the method includes,
at step 416, triggering an action in response to determining the
error condition so that appropriate remedial actions may be
taken.
[0129] In one alternative, the method optionally includes defining
a second motor operation for the instrument when the instrument
tool tip is in contact with the bone. Similar to the first motor
operation for the instrument when the instrument tool tip is not in
contact with the bone, data representing the operating parameters
of the second motor operation may comprise at least one of the
power, the voltage, the current, the rotational speed, or other
operating parameter, or combination of parameters, that
characterizes the operation of the motor while in contact with the
bone. This data representing the second motor operation can be
stored in the memory of the controller controlling the operation of
the surgical instrument. Alternatively, or in addition, the data
can be communicated by the controller to the navigation system. In
a further alternative or addition, the data can be stored on a
memory incorporated into the surgical instrument itself.
[0130] Defining a second motor operation for when the surgical
instrument is in contact with the bone, the method can include
determining a second error condition when the monitored position of
the instrument tool tip is not in contact with the bone in the
localizer coordinate system but the motor operation is equal to the
second defined motor operation--being the motor operation for when
the instrument tool tip is in contact with the bone. Upon
determining the second error condition is present, the method can
include triggering a second action so that appropriate corrective
action can be taken.
[0131] With regard to either error condition discussed above, the
resulting action can include one or more of sounding an audible
alert, displaying a visual alert, activating a tactile alert,
cutting off power to the surgical instrument, or combinations
thereof. Sounding an audible alert can include any kind of sound
alarm, beep, buzzer or the like. Displaying a visual alert may
include displaying a prompt on one or more of the displays of the
navigation system that indicates the nature of the error condition
determined. A visual alert may also include illuminating a light,
such as an LED light on the surgical instrument itself. The visual
alert may include any other visible type indication that an error
condition has been determined. Activating a tactile alert may
include energizing a vibratory feature of the instrument or the
footswitch. The vibration may be characterized as a pattern of
vibrations associated with the type of error so that the user can
distinguish among different types of errors based on the type of
vibration alone.
[0132] Illustrated in FIG. 5 is a second method 500 of navigating a
surgical instrument having a variable speed motor relative to a
bone and determining a tool-to-bone offset. The second method 500
is similar in some respects to the first method 400 described
above. Steps of the second method 500 may be defined in relation to
the steps of the first method 400 where such similarity exists.
Specifically, the second method 500 employs a navigation system,
surgical instrument, instrument tracker and patient tracker similar
to the method 400. Likewise, a controller is in communication with
the navigation system and provides power to the surgical
instrument.
[0133] The second method 500 begins with the same steps 502, 504 of
registering the patent tracker to the bone and the instrument
tracker to the surgical instrument as steps 402 and 404. The second
method 500, also includes the step 506, of defining a first motor
operation for the surgical instrument while the instrument is not
in contact with the bone, which is the same as step 406 described
above. Further similar to the first method 400, the second method
500 includes the steps 508 and 510 of monitoring the motor
operation with the controller and monitoring the position of the
instrument tool tip relative to the bone with the navigation
system, as in steps 408 and 410.
[0134] Deviating from the first method 400, the second method 500
includes comparing the monitored motor operation to the defined
first motor operation at step 512. This comparison can be performed
repeatedly over time on a continuous cycle at some frequency during
the course of the operation. The second method 500 also includes
determining, at step 514, as a result of the comparison at step
512, a contact time between the instrument tool tip and the bone
when the monitored motor operation deviates from the defined first
motor operation. When the continuously monitored characteristic of
the motor operation changes from the defined first motor
operation--representing the motor operation when the instrument is
not in contact with the bone--the time of contact between the
instrument and the bone can determined.
[0135] Once the time of contact between the instrument and the bone
has been determined at step 514, the second method 500 includes, at
step 516, determining with the navigation system, at the contact
time, a tool-to-bone offset as a distance between the instrument
tool tip and a surface of the bone in the localizer coordinate
system. The navigation system monitoring the position of the
instrument tool tip and the bone can receive a signal from the
instrument controller indicating the contact between the tool tip
and the bone, based on the determination by the controller that the
monitored motor operation has deviated from the first defined motor
operation when the instrument is not in contact with the bone.
[0136] Given the time of contact, the navigation system evaluates
the tracked positions of the tool tip and the bone and computes a
distance between the closest points of the tool tip and the surface
of the bone in the localizer coordinate system, when the navigation
system calculates that the tool tip is separated from the bone. In
another case, the navigation system may calculate that the tool tip
is penetrating into the bone by some distance given the time of
contact based on the controller determining a deviation from the
defined motor operation. In this case, the navigation system
computes a distance normal to the surface of the bone of the
maximum penetration depth of any point of the tool tip. In either
case, the calculated distance is the tool-to-bone offset. Said
differently, the tool-to-bone offset is a measure of the margin of
accuracy between the true physical position of the tool relative to
the bone and the virtual representations of the position of the
tool relative to the bone.
[0137] As described above, there are a number of factors that can
introduce or increase a tool-to-bone offset. If a tracker is
displaced or deformed after it has been registered, it can lead to
a decrease in the navigation accuracy. Likewise, if the navigation
cart assembly is jostled or bumped during the operation, causing
the camera unit to shift, that can also lead to a decrease in the
navigation accuracy. Other factors can include tool wear, tool
deformation, or gross removal of tissue from the bone. It is
preferable to maintain a low tool-to-bone offset in maintaining a
consistent and highly accurate navigation.
[0138] If the tool-to-bone offset increases too high, the accuracy
of the navigation guidance may be compromised and require remedial
action. The second method 500 therefor includes the step 518 of
triggering an action when the tool-to-bone offset exceeds a
predefined magnitude. In one example, the predefined magnitude is
0.5 millimeters. That is, when the instrument contacts the bone, as
determined by a deviation in the motor operation monitored by the
controller, the navigation system calculates that the tool tip is
0.5 millimeters from the surface of the bone. Although described
with reference to a specific magnitude, this is not intended to be
limiting, and other limits are contemplated. Moreover, different
limits may be applicable to different tools or different
applications of the same tool. This step 518 of triggering an
action is similar to the step 416 of triggering an action in
response to determining an error condition. The resulting action
can include one or more of sounding an audible alert, displaying a
visual alert, activating a tactile alert, cutting off power to the
surgical instrument, or combinations thereof, as described
above.
[0139] In order to provide information to the user, the second
method 500 may further include the step of displaying on a display
of the navigation system the value of the tool-to-bone offset. This
can allow the user to track and monitor the accuracy of the
navigation guidance being provided by the navigation system. In
implementing this method in a surgical operation, the step of
determining the value of the tool-to-bone offset may be repeated
multiple times throughout the procedure, for example, each time the
controller determines a time of contact between the instrument and
the bone based on a deviation in the motor operation. Thus, the
display of the tool-to-bone offset may be a continuously updated
value for each time the determination is performed. In addition to
a numerical presentation of the value of the tool-to-bone offset,
this information may also, or alternatively, be displayed as a
chart, or line graph, of values over time.
[0140] To further assist the user, the value of the tool-to-bone
offset may be displayed differently based on the magnitude. For
example, lower magnitudes, indicating a low tool-to-bone offset and
a high degree of accuracy in the navigation guidance, may be
displayed in a first color, whereas higher magnitudes may be
displayed in a second color, different from the first color. Yet
further, even higher magnitudes may be displayed in a third color,
different from the first and the second colors. Other color
combinations or visual representations may also be employed in this
same way.
[0141] To facilitate this dynamic display of the tool-to-bone
offset value, the second method 500 may include the step of
defining a first level magnitude and a second level magnitude.
These first and second level magnitudes may be predefined in the
system as default values. Alternatively, the first and second level
magnitudes may be entered by the user at the start of the operation
or during a set up operation of the system. In one example, the
first level magnitude may be 0.25 millimeters and the second level
magnitude may be 0.4 millimeters.
[0142] In one example, when the tool-to-bone offset is calculated
to be less than the first level magnitude, the displayed value may
be presented in a green color. When the tool-to-bone offset is
calculated to be less than the second level magnitude, the
displayed value may be presented in a yellow color. When the
tool-to-bone offset is above the second level magnitude the
displayed value may be presented in a red color. These color
designations are not intended to be limiting and are only intended
to illustrate one example. In another case, the dynamic display of
the tool-to-bone offset may utilize variable size, in the
alternative or in addition to changing the color of the displayed
value.
[0143] The first and second level magnitudes of the tool-to-bone
offset value may also be utilized for triggering one or more of the
actions at step 518 of the second method 500. For example, upon the
tool-to-bone offset reaching or exceeding the first level magnitude
a visual alert may be triggered, and upon the tool-to-bone offset
reaching or exceeding the second level magnitude, a combination of
visual and audible alerts may be triggered.
[0144] Additionally, a third level magnitude may also be defined in
the same or a different manner as the first and second level
magnitudes. The third level magnitude may represent the value of
the tool-to-bone offset where the system determines to disable
power from the controller to surgical instrument. When the
tool-to-bone offset reaches the third level magnitude, the accuracy
of the navigation system may be compromised to the point that risk
of harm is present and so the surgical instrument must be disabled
until remedial action is taken.
[0145] As described above, the navigation system may alert the user
to a condition where remedial action is required to improve the
accuracy of the navigation guidance in response to certain errors
or to determined values of the tool-to-bone offset. There are a
number of different remedial actions that are possible, and the
proper correction may depend on the specific error encountered. In
one example, if an error condition arises from a broken or worn
tool, the remedial action would be to replace the tool. In another
example, if an error condition arises from displacing a tracker
from its relationship to the associated tracked object, or if the
navigation cart assembly is jostled or bumped, re-registration of
the trackers to the object in the localizer coordinate system may
be appropriate remedial action.
[0146] In another example, in a surgical operation where a
substantial amount of tissue is removed, the virtual representation
of the anatomy will no longer represent the patient's actual
anatomy. To remedy this situation, additional imaging, modeling,
and registration may be necessary to redefine the location of
tissue surfaces within the virtual representation of the anatomy.
In one example, the surgical instrument may be unpowered and used
as a pointer to touch off of multiple points on the resected
surface of the anatomy to create a new point cloud for the
navigation system to redefine the surface of the virtual
representation of the bone.
[0147] The disclosed methods may be practiced with an improved
surgical system, as shown in FIGS. 1 and 2, and described above in
various configurations. The surgical system comprises a surgical
instrument having a variable speed motor and a tool tip. The
surgical instrument is in operative communication with a controller
for providing power to the surgical instrument. The controller is
further operable to monitor a motor operation of the instrument and
comprises a processor and a memory operable to store information,
including information representing the monitored motor operation.
The system also comprises an instrument tracker coupled to the
instrument and a patient tracker to be coupled to a patient's
anatomy.
[0148] The surgical system also comprises a navigation system. The
navigation system includes a localizer and a navigation computer.
The navigation computer includes a processor and a memory to store
information, including information representing the surgical
instrument, and information representing the patient's anatomy, in
a virtual space and relative to a localizer coordinate system
within the virtual space. The navigation system is operable to
track the location of the instrument and the bone in virtual space
during the operation based on information gathered by the
localizer. The localizer is operable to register the location of
the instrument tracker and the location of the patient tracker
relative to a localizer coordinate system and to gather information
about the location of the instrument and the bone in cooperation
with the instrument tracker and the patient tracker
respectively.
[0149] The controller and the navigation system are in electronic
communication and configured to cooperate with each other. In
operation, the controller and the navigation system determine a
time of contact between the tool tip and the bone based on a change
in the motor operation of the instrument. The controller and the
navigation system also determine, at the time of contact, a
tool-to-bone offset as a distance between the tracked location of
the tool top and the tracked location of the bone.
[0150] The surgical system may further comprise an alert device.
The controller and the navigation system are in further
communication with the alert device and operate to trigger an
action when the tool-to-bone offset is greater than a predefined
magnitude. The alert device may include a visual alert device such
as lights or displays on the console 82, the computer cart assembly
24, on the camera unit 36, or elsewhere in the operating
environment. Other visual alerts may take the form of prompts for
user action, information displays, or other shapes, forms, pictures
or otherwise. The alert device may include an audible alert device
such as a speaker, bell, horn, buzzer or the like. Other audible
alerts may include tones, alarms, prerecorded messages or
otherwise. The alert device may include a haptic alert device
capable of generating a tactile alert perceptible to the user, such
as through vibration.
[0151] In a configuration where trackers are properly registered to
the surgical instrument and to the patient's anatomy, a user may
place an unpowered tool tip of the surgical instrument in contact
with the patient's anatomy, and the navigation system will
correctly determine that the tool tip is in contact with the
patient's anatomy in the common coordinate system, without any gap
or overlap. However, it is possible for the trackers, the surgical
instrument, or the anatomy to deflect or deform, or the camera unit
of the navigation system to be disturbed, in a way the causes the
registration to become inaccurate. Therefore, it is desirable to
provide a method for the navigation system to perform a
registration verification operation that does not require the tool
to be powered and thus does not rely on any parameter of the tool
operating in free space or in contact with a patient's anatomy. The
user may place the tool tip of the surgical instrument in
stationary contact with the patient's anatomy, in an unpowered
state so that the anatomy is not affected by the tool and hold that
position to trigger the navigation system to perform a registration
verification.
[0152] Illustrated in FIG. 9, a method 600 of operating a surgical
navigation system during a surgical operation to verify a tracking
registration is provided. In the method 600, the surgical
navigation system, as described above, includes a localizer having
a localizer coordinate system, an instrument tracker coupled to the
surgical instrument, and a patient tracker coupled to the patient's
anatomy--for example, a vertebra, other bone, or soft tissue.
References to a patient's anatomy, a specific bone, or bone in
general, should be read broadly to include soft tissue and other
non-bone applications. The method 600 uses a controller
communicating with the navigation system and controlling the
surgical instrument.
[0153] In a first step 602 of the method 600, the user registers
the patient tracker to the bone. Registering the patient tracker
relates the patient tracker coordinate system to the localizer
coordinate system or other common coordinate system. This step also
defines the location and the orientation of the bone relative to
the patient tracker so that the navigation system can track and
monitor the position and orientation, or pose, of the bone based on
the detected movement of the patient tracker and updating the
virtual representation of the anatomy in the navigation system.
[0154] In a second step 604 of the method 600, the user registers
the instrument tracker to the surgical instrument. Registering the
instrument tracker relates the instrument tracker coordinate system
to the localizer coordinate system or other common coordinate
system. This step 604 also defines the position and orientation of
the instrument tool tip relative to the instrument tracker so that
the navigation system can track and monitor the position and
orientation, or pose, of the instrument tool tip based on the
detected movement of the instrument tracker and updating the
virtual representation of the instrument in the navigation
system.
[0155] The method 600 includes the steps 606, 608 of monitoring,
with the navigation system, the pose of the anatomy and the
location of the surgical instrument over time and tracking the pose
of the anatomy and the instrument with a virtual representation
which can be displayed to the user. Monitoring the location of the
patient's anatomy and the surgical instrument includes monitoring
both the position and orientation of the tracked objects. The
position and orientation are monitored over time on a continuous
cycle at a frequency during the course of the operation. With this
information, the navigation system can determine velocity,
acceleration, and other quantities, including magnitude and
direction of motion in the common coordinate system, and relative
to other tracked objects.
[0156] The method 600 includes the step 610 of determining that the
tool tip of the surgical instrument is statically positioned within
a predefined proximity to the patient's anatomy. In this step, the
navigation system monitors the velocity of the tool tip relative to
the anatomy, in addition to monitoring the position of the tool tip
and of the anatomy. During the operation, the user places the tool
tip in contact with the bone, while the tool is not powered, in
order to prompt the navigation system to verify the registration of
the trackers on the surgical instrument and patient's anatomy.
[0157] Because the registration is susceptible to error, the
navigation system may evaluate the registration verification when
the tool tip is determined by the navigation system to be
stationary within a predefined proximity with the patient's
anatomy. The navigation system may determine that the tool tip is
stationary when the tracked position does not change for a
predetermined period of time. The predetermined period of time may
be preprogrammed to the navigation system to be, for example, three
seconds, five seconds, or other duration. The predefined proximity
may be, for example, about 3 millimeters, about 1 millimeter, or
about 0.5 millimeter. The predefined proximity may be some other
distance value suitable to the level of precision measurable by the
navigation system. During a configuration of the navigation system,
such as during start up prior to the surgical operation, a user may
be prompted to select a duration for the predetermined period of
time or a distance for the predefined proximity from a list of
options, or else may be prompted to enter a duration or distance
through a touch pad, button selection, touchscreen or other
input.
[0158] The navigation system may determine that the tool tip is
stationary when the tracked position and orientation of the tool
tip is static and does not change during the predetermined period
of time. Alternatively, the position may be determined to be
stationary when the position and orientation does not change by
more than a specific magnitude. Further alternatively, the position
may be determined to be stationary when the position and
orientation does not change, or else does not change by more than a
specific magnitude in a specific direction, such as where the
specific direction is in the direction toward the anatomy.
[0159] Once the navigation system determines that the tool tip is
stationary in a static position and orientation in proximity to the
bone, the method 600 includes the step 612 of determining an offset
distance. The offset distance is a measure of the inaccuracy in the
system. The navigation system receives the input from the user
indicating that the tool tip is in static contact with the anatomy
and evaluates the tracked positions of the instrument tool tip and
the patient's anatomy. The result of this evaluation, based on the
tracked positions, may calculate that the tool tip is separated
from the bone by a distance, or may calculate that the tool tip is
penetrating into the bone by a distance, based on the tracked
positions and orientations of the virtual representations of the
surgical instrument and the patient's anatomy. The magnitude of the
calculated distance defines a tool-to-bone offset and indicates the
margin of accuracy between the true physical position of the tool
tip relative to the anatomy and the virtual representations of the
tool tip relative to the anatomy in the navigation system.
[0160] In calculating the offset distance, the navigation system
identifies a first point on the virtual representation of the
surgical instrument that is either the closest proximal point to
the virtual representation of the patient's anatomy, or else is the
point of deepest penetration or overlap of the virtual
representation of the surgical instrument into the virtual
representation of the patient's anatomy. Where the first identified
point of the instrument is outside the anatomy, the offset distance
is the shortest distance between the first identified point and
some point on the surface of the virtual representation of the
anatomy such that the offset distance is normal to the surface and
directed outward. Where the first identified point of the
instrument is internal to the virtual representation of the
anatomy, the offset distance is the greatest distance between the
first identified point and some point on the surface of the virtual
representation of the anatomy such that the offset distance is
normal to the surface and directed inward.
[0161] Once an offset distance is determined, the navigation system
in the method 600, at step 614 compares the calculated offset
distance to a predefined threshold for allowable system inaccuracy.
If the offset distance is greater than the predefined threshold,
indicating a lower level of accuracy than desired, the navigation
system may be configured to trigger an action in response. In one
example, the predefined threshold is 0.5 millimeters. That is, when
the tool tip is in static contact with the anatomy, as determined
by navigation system based on the tracked positions, the navigation
system calculates that the virtual representation of the tool tip
is 0.5 millimeters from the virtual representation of the anatomy.
Although described with reference to a specific magnitude, this is
not intended to be limiting, and other limits are contemplated.
Moreover, different limits may be applicable to different tools or
different applications of the same tool. The triggered action can
include one or more of sounding an audible alert, displaying a
visual alert, activating a tactile alert, disabling power to the
surgical instrument, or combinations thereof, and as described
above.
[0162] The predefined threshold may include multiple values
indicating different levels of accuracy, where different actions
are triggered depending on how the offset distance compares with
the different values. For example, the predefined threshold may
include a first predefined threshold and a second predefined
threshold. Triggering an action may include triggering a first
action when the offset distance is greater than the first
predefined threshold and triggering a second action when the offset
distance is greater than the second predefined threshold. The
actions may include any action as described above to include
audible alerts, visual alerts, tactile alerts, or various
combinations thereof.
[0163] The method 600 illustrated in FIG. 9, may be expanded as
illustrated in FIG. 10 as method 620. In one expansion, the
navigation system, at step 622, may prompt the user to initiate a
registration verification cycle as detailed in method 600 above.
The prompt may be presented to the user as a visual prompt, such as
by showing a message on a display. Alternatively, a visual prompt
may include a flashing light, or otherwise. The prompt may be
presented to the user as an audible prompt, such as by a tone,
beep, prerecorded message, or the like. The prompt may be presented
as a haptic prompt, such as by a prescribed series or cycle of
vibrations. The prompt may be presented to the user as a
combination of visual, audible, or haptic prompts.
[0164] The method 620 includes step 624 of determining a first
offset with the surgical instrument in a first pose. This step is
performed consistent with the steps of method 600, shown in FIG. 9,
with the static position of the tool tip comprising the first
pose--position and orientation of the surgical instrument. The
method 620 includes step 626 of determining a second offset in a
second pose. This requires changing the position, orientation, or
both, of the surgical instrument and placing the tool tip in static
contact with the anatomy a second time. With the tool tip in static
contact with the anatomy in a second pose, the navigation system
determines a second offset value. The navigation system may
therefore evaluate the tool-to-bone offset in this way from more
than one angle to ensure the accuracy of the system in multiple
angles.
[0165] Having determined first and second offsets from the first
and second poses respectively in steps 624, 626, the navigation
system compares the first and second offsets with an allowed
threshold at step 628. In this step, the navigation system may
independently compare the first offset with the allowed threshold
and compare the second offset with the allowed threshold and may
trigger an action if either one or the other of the first and
second offsets are over the allowed threshold. The step 630 of
triggering an action may be similar to step 616 of triggering an
action.
[0166] Once an action is triggered in response to the navigation
system determining that an offset is over an allowed threshold, the
user may have the opportunity to enter an input to maintain system
operation without taking other corrective action such as
re-registering the trackers to the surgical instrument or to the
patient's anatomy. The navigation system may receive an input to
override or cancel the action triggered by the offset being greater
than the allowed threshold at step 631. The navigation system may
receive an input, such as a voice command, a gesture input, or
other input through a keypad, touchscreen, or the like. Receiving
the input to override or cancel the triggered action, the
navigation system, and the surgical instrument, may return to
normal operation.
[0167] FIG. 11 illustrates method 632 as an alternative, or an
addition, to step 628 of method 620 of comparing the first and
second offsets to an allowed threshold. Once the navigation system
has determined the first and second offsets in first and second
poses, as in step 634, the navigation system may calculate a
three-dimensional offset based on the first and second offsets and
on the geometric relationship between the first and second poses,
or more specifically, on the geometric relationship between the
specific points of contact on the surface of the tool tip applied
in static contact with the anatomy in the first and second poses.
Once the three-dimensional offset value is determined, the
navigation system may compare the three-dimensional offset with an
allowed threshold, at step 638. The allowed threshold may be the
same magnitude or a different magnitude as compared to the allowed
threshold when comparing one of the first or second offsets. If the
offset is over the allowed threshold, the method includes
triggering an action at step 640.
[0168] As a further alternative, the methods 620 and 632, may
additionally include determining a third offset in a third pose. In
step 628 of method 620, comparing the first and second offset with
an allowed threshold may include comparing the third offset with
the allowed threshold. Likewise, in method 632, step 634 may
include determining a third offset in a third pose in addition to
determining the first and second offsets in the first and second
poses. Further, in step 636, the navigation system may calculate
the three-dimensional offset based on the first, second, and third
offsets and the geometric relationships between the first, second
and third poses, or first, second and third points of contact
between the tool tip and the anatomy in the first, second, and
third poses.
[0169] Calculating the three-dimensional offset depends on the
geometry of the tool tip. In a first example, as illustrated in
FIG. 12, the tool tip 180 may include a substantially cylindrical,
tapered, rounded-conical, or elongated aspect 182, such as with a
drill bit or router. The elongated aspect 182 of the tool tip 180
may define a longitudinal axis L extending through a center and
parallel with the elongated aspect 182. When placed in static
contact with the anatomy, such as vertebra V, for verifying the
registration and determining an offset value, the point of contact
184 between the tool tip 180 and the anatomy V is, for example,
along the peripheral edge 186 at the end of the elongated aspect
182 at a distance from the longitudinal axis equal to the radius of
the elongated aspect.
[0170] In another example, as illustrated in FIG. 13, the tool tip
190 may include a substantially spherical aspect 192, such as with
a round bur. The spherical aspect 192 of the tool tip 190 may
define a centerpoint 194 at the center of the spherical aspect.
When placed in static contact with the anatomy, such as a vertebra
V for verifying the registration and determining an offset value,
the point of contact 196 between the tool tip 190 and the anatomy V
is, for example, on the surface of the spherical aspect 192 at a
distance from the centerpoint 194 equal to the radius of the
spherical aspect 192.
[0171] Determining a three-dimensional offset, such as at step 636
of the method 632, illustrated in FIG. 11, requires determining a
first offset with the surgical instrument at a first pose with
respect to the anatomy, a second offset at a second pose, and
optionally, a third offset at a third pose. Placing the surgical
instrument in multiple different poses presents a different view of
the surgical instrument tracker to the camera unit of the
localizer. The multiple views ensure that any registration error is
able to be discerned by the navigation system and is not concealed
by a particular view of the instrument.
[0172] To ensure sufficient differentiation in the views of the
surgical instrument by the navigation system, there should be
sufficient rotation of the surgical instrument from one pose to the
next. For example, establishing a first offset distance at a first
pose, the surgical instrument may be rotated so that the point of
contact on the tool tip is about 90.degree. away in the second pose
from the point of contact on the tool tip in the first pose. As
illustrated in FIG. 12, where the tool tip 180 has an elongated
aspect 182, the second point of contact 188 may be about 90.degree.
from the first point of contact 184 via a rotation about the
longitudinal axis L of the tool tip 180. As illustrated in FIG. 13,
where the tool tip 190 has a spherical aspect 192, the second point
of contact 198 may be about 90.degree. from the first point of
contact 196 via a rotation about the centerpoint 194 in any plane.
Where a third offset distance is determined, a third point of
contact 189, 199 in the third pose may be about 90.degree. away
from the first 184, 196 and the second 188, 198 points of contact
in the first and second poses, respectively.
[0173] During the course of a surgical operation, the surgical
instrument may be applied in contact with more than one bone, such
as multiple vertebrae along a spine. At an initial phase of the
surgical operation, trackers may be registered to each of the
individual bones that will be affected by the operation.
Transitioning from operating on one bone to operating on a second
bone, a user may verify the registration of the tracker of the
second bone following completion of the surgical intervention on
the first bone. The user can trigger the navigation system to
verify the tracking registration process by positioning the tool
tip in static contact with the second bone. Alternatively, the
navigation system, upon completion of a phase of the surgical plan
applied to the first bone, may prompt the user to verify the
registration before beginning the surgical intervention according
to a surgical plan for the second bone.
[0174] The navigation system may designate a portion of the bone to
contact with the tool tip for the registration verification. The
portion of the bone designated for the registration verification
may be an exposed portion of the bone that nonetheless is not
targeted for resection according to the surgical plan. Selecting a
portion not targeted for surgical intervention increases the
likelihood that the bone surfaces match the virtual representation
of the patient's anatomy to provide an accurate basis for verifying
the tracker registration. The navigation system may display a
graphical representation of the patient's anatomy with a particular
portion highlighted, flagged, indicated with an arrow, outline, or
other signifier to identify the portion of the anatomy to the
user.
[0175] The above description is provided in an illustrative manner.
It is to be understood that the terminology which has been used is
intended to be in the nature of words of description rather than of
limitation. Many modifications and variations are possible in light
of the above teachings. Therefore, within the scope of the appended
claims, features or implementations may be practiced other than as
specifically described.
Clauses
[0176] I. A surgical system comprising: [0177] a surgical
instrument having a variable speed motor and a tool tip; [0178] a
controller for providing power to the surgical instrument, the
controller operable to monitor a motor operation of the instrument,
the controller comprising a processor and a memory, the memory
operable to store information, including information representing
the motor operation of the instrument; [0179] an instrument tracker
coupled to the instrument; [0180] a patient tracker to be coupled
to a bone; and [0181] a navigation system comprising a localizer;
[0182] the navigation system operable to store information
representing the surgical instrument, and information representing
the bone, in a virtual space; [0183] the localizer operable to
register a location of the instrument tracker and a location of the
patient tracker relative to a localizer coordinate system, and to
gather information about the location of the instrument and the
bone in cooperation with the instrument tracker and the patient
tracker, respectively; [0184] the navigation system operable to
track the location of the instrument and the location of the bone
in the virtual space based on information gathered by the
localizer; [0185] wherein the controller and the navigation system
are in electronic communication and configured to cooperate to:
[0186] determine, based on a change in the motor operation, a time
of contact between the tool tip and the bone; and [0187] determine,
at the time of contact, a tool-to-bone offset as a distance between
the tracked location of the tool tip and the tracked location of
the bone. [0188] II. The surgical system of clause I, wherein
monitoring the motor operation comprises one of monitoring a power
level, a voltage level, a current level, or combinations thereof,
and wherein the motor operation comprises a first motor operation
when operated while the tool tip is not in contact with bone and a
second motor operation, different from the first motor operation,
when operated while the tool tip is in contact with bone. [0189]
III. The surgical system of any of clauses I-II, further comprising
an alert device, wherein the controller and the navigation system
are further configured to trigger an action when the tool-to-bone
offset is greater than a predefined magnitude. [0190] IV. The
surgical system of clause III, wherein triggering the action
comprises one of sounding an audible alert, displaying a visible
alert, activating a tactile alter, cutting off power to the
surgical instruments, or combinations thereof. [0191] V. The
surgical system of any of clauses III-IV, wherein the predefined
magnitude is 0.5 millimeters. [0192] VI. The surgical system of any
of clauses III-V, wherein the predefined magnitude comprises a
first predefined magnitude and a second predefined magnitude,
different from the first predefined magnitude, and wherein the
controller and the navigation system are configured to trigger a
first action when the tool-to-bone offset is greater than a first
predefined magnitude and a second action, different from the first
action when the tool-to-bone offset is greater than a second
predefined magnitude. [0193] VII. The surgical system of any of
clauses I-VI, wherein the controller and the navigation system are
configured to cooperate to determine each occurrence of a change in
motor operation during a medical procedure; determine a time of
contact for each occurrence of the change in motor operation;
determine, for each time of contact, a tool-to-bone offset; and log
a series of determined tool-to-bone offsets. [0194] VIII. The
surgical system of any of clauses I-VI, further comprising a
display device in electronic communication with one of the
controller, the navigation system, or the combination of the
controller and the navigation system, and wherein the controller,
the navigation system or the combination of the controller and the
navigation system are further configured to cause the display
device to display the determined tool-to-bone offset. [0195] IX.
The surgical system of clause VIII, wherein the controller, the
navigation system or the combination of the controller and the
navigation system are further configured to cause the display
device to display the series of determined too-to-bone offsets as a
serially updating value. [0196] X. A surgical system comprising:
[0197] a surgical instrument having an actuator and a tool tip;
[0198] a controller for providing power to the surgical instrument,
the controller operable to monitor an actuator operation of the
instrument, the controller comprising a processor and a memory, the
memory operable to store information, including information
representing an actuator operation of the instrument; [0199] an
instrument tracker coupled to the instrument; [0200] a patient
tracker to be coupled to a tissue; [0201] a navigation system
comprising a localizer; [0202] the navigation system operable to
store information representing the surgical instrument, and
information representing the tissue, in a virtual space; [0203] the
localizer operable to register a location of the instrument tracker
and a location of the patient tracker relative to a localizer
coordinate system, and to gather information about the location of
the instrument and the tissue in cooperation with the instrument
tracker and the patient tracker, respectively; [0204] the
navigation system operable to track the location of the instrument
and the location of the tissue in the virtual space during
operation based on information gathered by the localizer; [0205]
wherein the controller and the navigation system are in electronic
communication and configured to cooperate to: [0206] determine,
based on a change in the actuator operation, a time of contact
between the tool tip and the tissue; and [0207] determine, at the
time of contact, a tool-to-bone offset as a distance between the
tracked location of the tool tip and the tracked location of the
tissue. [0208] XI. A surgical system comprising: [0209] a
navigation system comprising a control console and a localizer;
[0210] the navigation system in communication with first data
representing a surgical instrument, the surgical instrument
including a tool tip, and second data representing a patient's
anatomy; [0211] the navigation system operable to track the
surgical instrument and the anatomy in a virtual space during a
surgical operation based on information gathered by the localizer
from an instrument tracker coupled to the surgical instrument and a
patient tracker coupled to the anatomy; [0212] wherein the
navigation system is configured to: [0213] track the surgical
instrument and the anatomy and store data representing the tracked
surgical instrument pose and the anatomy pose in a common
coordinate system; [0214] determine the tool tip is within a
predefined proximity to the anatomy based on the tracked surgical
instrument pose and the tracked anatomy pose; [0215] determine the
tool tip does not depart the predefined proximity by more than a
predefined magnitude over a predefined duration; [0216] determine
an offset distance based on the tracked surgical instrument and the
tracked anatomy in the common coordinate system; and [0217] compare
the offset distance to a predefined threshold. [0218] XII. The
surgical system of clause XXI, further comprising an alert device,
wherein the navigation system is further configured to trigger an
action when the offset distance is greater than the predefined
threshold. [0219] XIII. The surgical system of clause XII, wherein
the alert device is a footswitch, wherein the footswitch is
operable to generate a vibration; and wherein the action is a
vibration of the footswitch. [0220] XIV. The surgical system of
clause XII, wherein the action comprises one of sounding an audible
alert, displaying a visible alert, activating a tactile alter,
cutting off power to the surgical instrument, or combinations
thereof. [0221] XV. The surgical system of any of clauses XII-XIV,
wherein the predefined threshold is 0.5 millimeters. [0222] XVI.
The surgical system of any of clauses XII-XIV, wherein the
predefined magnitude comprises a first predefined magnitude and a
second predefined magnitude, different from the first predefined
magnitude, and wherein the navigation system is configured to
trigger a first action when the offset distance is greater than a
first predefined magnitude and a second action, different from the
first action when the offset distance is greater than a second
predefined magnitude. [0223] XVII. The surgical system of any of
clauses XII-XVI, further comprising a display device in electronic
communication with the navigation system, and wherein the
navigation system is further configured to cause the display device
to display the determined offset distance. [0224] XVIII. The
surgical system of clause XVII, wherein the offset distance is
displayed in a first color when the offset distance if less than
the predefined threshold and is displayed in a second color,
different from the first color, when the offset distance is greater
than the predefined threshold. [0225] XIX. A method of performing a
surgical operation, the method comprising: [0226] coupling a
patient tracker to a patient's anatomy; [0227] coupling an
instrument tracker to a surgical instrument, the surgical
instrument including a tool tip; [0228] operating a navigation
system to register the instrument tracker and the patient tracker
in a common coordinate system and to track the surgical instrument
and the patient's anatomy; [0229] pausing the tool tip in contact
with the anatomy for a predefined duration to initiate a
registration verification; [0230] wherein the navigation system is
configured to determine an offset distance based on the tracked
surgical instrument and the tracked patient's anatomy; and [0231]
evaluating the offset distance against a predefined threshold.
[0232] XX. The method of clause XIX, wherein the navigation system
is configured to trigger an action when the offset distance is
greater than the predefined threshold, wherein the action includes
one of sounding an audible alert, displaying a visual alert,
activating a tactile alert, cutting off power to the surgical
instrument or combinations thereof. [0233] XXI. The method of
clause XX, further comprising providing an input to the navigation
system to terminate the triggered action. [0234] XXII. The method
of clause XIX, wherein the patient's anatomy includes a first bone
and a second bone; the method further comprising: [0235] operating
the surgical instrument in application to the first bone; [0236]
operating the surgical instrument in application to the second
bone; and [0237] wherein pausing the tool to initiate a
registration verification is performed in contact with the second
bone subsequent to operating the surgical instrument in application
to the first bone and prior to operating the surgical instrument in
application to the second bone.
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